Standard for Connection of Embedded Generating Systems 5MW and below in the Ergon Energy Distribution Network

Transcription

1 Standard Standard for Connection of Embedded Generating Systems 5W and below in the Ergon Energy Distribution Network This Standard is created and made available for use for the construction of certain embedded generating systems that will interconnect with Ergon Energy s distribution network. These are general requirements only and the use of this Standard is at your own risk and discretion. If this standard is a printed version, please download the latest version from Ergon Energy s website ( to ensure compliance. Approver Jason Hall Asset anagement Group anager Engineering Standards & Technology If RPEQ sign off required insert details below. Ergon Energy Certified Person name and Position Carmelo Noel Engineering anager Distribution Network Standards Registration Number 8802 Rob Coggan Protection Engineering anager Jenny Gannon Senior Network Strategy & Policy Engineer Abstract: This standard provides the requirement for connecting EG to operate in parallel with Ergon Energy s distribution network not exceeding 5W. Keywords: embedded generation, generator, inverter systems

2 Foreword This Standard has been prepared by Ergon Energy to provide owners and Proponents of embedded generation (EG) installations information about their rights and obligations for the connection to and interfacing with. Embedded generating systems are defined in the National Electricity Rules as generating units connecting directly to the distribution network and not the transmission network. The National Electricity Rules also identify the requirements for generating systems connected to transmission and/or distribution systems and, in part, requires that a person must not engage in the activity of owning, controlling or operating a generating system connected to the interconnected transmission or distribution system unless: The person is a Registered Participant; or The person is exempt from the requirement to be a Registered Participant. AEO has decided that a person who engages in the activity of owning, controlling, or operating a generating system that satisfies any of the following conditions, is automatically exempt from the requirement to register as a Generator in relation to that activity where both (a) and (b) apply: (a) one of the following applies: (i) the embedded generating system has a total nameplate rating at a connection point of less than 5 W; or (ii) the embedded generating system is not capable of exporting to a transmission system or distribution system in excess of 5 W; or (iii) the embedded generating system has no capability to synchronise or to operate electrically connected to a distribution system or transmission system; and (b) either: (i) the sent out generation of the generating unit is purchased in its entirety by the local retailer or by a customer located at the same connection point; or (ii) each of the generating units comprising the generating system is classified as a market generating unit by a market small generation aggregator. If you are unsure whether your Embedded Generating System meets both of these criteria, you may submit an Application for Exemption from Registration as a Generator, which is for a specific exemption, for AEO s consideration. Please refer to this part of AEO s website for further information: Classification-Guides. Check this is the latest version before use. ii Standard STNW1165 Ver 5

3 Table of Contents 1. General Purpose Scope Application Enquiries References Ergon Energy controlled documents Other documents Definitions, Acronyms and Abbreviations Definitions Acronyms and Abbreviations Network Connection Overview Network Connection Agreement Connection Assets Technical Considerations Types of Embedded Generating Systems Export Embedded Generation Non-Export Embedded Generation Permissible Generating Unit Connection Arrangements Connection Enquiry and Application Process Technical Requirements and Performance Standards General Network Connection Arrangement and Voltage Level General Nominal Interconnection Voltage Power Frequency Network Characteristics Equipment Ratings Fault Levels and Protection Impacts Control System for Embedded Generating System General Requirements eans of Isolation Synchronising and Synchronising Check Facilities Generating System Control Reactive Power Check this is the latest version before use. iii Standard STNW1165 Ver 5

4 6.3.6 Fault Level Control Feeder Rating Feeder Reclosing Reconnection Protection System General Types of Protection Loss of ains (Lo) Synchronising Facilities Under/Over Frequency Under/Over Voltage Negative sequence voltage & current protection Overcurrent and earth fault protection Neutral Displacement protection Reverse power / power limit protection Rate of Change of Frequency (ROCOF) Remote or Transfer Trip (Intertripping) Protection Schemes General P1a Utility Feeder Protection P1b Substation Bus and Backup Protection P2 Remote Trip System P3 Distribution Substation HV Protection P4 Neutral Displacement Protection P5 HV Side UV OH Protection P6 Distribution Substation LV Protection P7 Synchronising Circuit Breaker Interlocks P8 Customer LV Protection P9 Embedded Generting System Protection P10 and P11 Fail Interlocks SCADA (Remote onitoring and Control) Earthing Requirements High Voltage Embedded Generating Systems Low Voltage Embedded Generating Systems Power Quality Power Factor Network Disturbance Limits Check this is the latest version before use. iv Standard STNW1165 Ver 5

5 7. Commissioning and Testing of Embedded Generation Plant Compliance onitoring and aintenance Notice of Alternation to Approved Design etering Installations aintenance Disputes Annex A Embedded Generation Connection Arrangements HV and LV Distribution33 Annex B Rotating Generating Unit Data Requirements Annex C Photovoltaic Inverter Energy System Data Requirements Annex D Protection of Embedded Generation Network Connections Introduction Short-Circuit Fault Considerations General Fault Currents Annex E Network Protection for Inverter Energy Systems with rating above 30 kva and less than 200 kva Annex F Network Protection for Inverter Energy Systems with rating above 200 kva Annex G SCADA Communication Requirements (inimum) Annex H Summary of NER Schedule 5.4 Connection Enquiry Check this is the latest version before use. v Standard STNW1165 Ver 5

6 1. General 1.1 Purpose The purpose of this Standard is to provide owners and Proponents of Embedded Generating system (EG) installations information about their rights and obligations for connection to and interfacing with the Ergon Energy s Network. This document is also intended to support the Registered Professional Engineer of Queensland (RPEQ) to design and commission EG for connection to Ergon Energy s Network. 1.2 Scope This Standard outlines the requirements for EG not exceeding 5W at a single connection point; that are intended to be connected to and operate in parallel with, any part of Ergon Energy s distribution network under normal operating conditions. This standard applies to the following: Synchronous generating units driven by hydro turbines; Synchronous generating units driven by gas engines, gas turbines or diesel engines. Inverter Energy Systems (>30 kva to 5 W) This does not apply to plant which is operated and connected in parallel with the network by Ergon Energy for the purpose of network or emergency support. 1.3 Application This Standard does not apply to: icro embedded generation unit via Inverters in the range up to 30 kva Larger generation over 5W Non-parallel back-up generation Ergon Energy Distribution Networks connected to Ergon Energy s 33 Isolated Power Stations. This document does not cover issues associated with the sale of electricity exported into the Ergon Energy distribution network. This is a matter between the proponent and their selected electricity retailer. 1.4 Enquiries Further information may be obtained by ing: majorconnections@ergon.com.au Check this is the latest version before use. Page 1 of 58 Standard STNW1165 Ver 5

7 2. References 2.1 Ergon Energy controlled documents Copies of Ergon Energy Standards may be obtained from the following website manuals-and-standards 2.2 Other documents Additional Australian Standards are listed in Ergon Energy s standard design documents. AS 2067 Substations and high voltage installations exceeding 1 kv ac AS/NZS 3000 Electrical installations (known as the Australian/New Zealand Wiring Rules) AS/NZS 3010 Electrical Installations Generating Sets AS 1931 Part 1 - High voltage - Test techniques - General definition and test requirements AS/NZS 3017 Electrical installations Testing Guidelines AS/NZS 3100 Approval and test specification - General requirements for electrical equipment AS 1319 Safety signs for occupational environment AS/NZS Series Electromagnetic compatibility (EC) AS/NZS 7000 Overhead line design Detailed Procedures AS 1359 General Requirements for Rotating Electrical achines AS Electric cables up to 36kV AS 2006 HV AC Switchgear & Control Gear CBS Greater than 1000V AS 2184 Low voltage switchgear AS 2373 Electric Cables Twisted Pair (For control and protection) AS 2374 Power Transformers IEC Series Protection Relays AS Rotating Electrical achines Part 22 AS/NZS Series Instrument Transformers AS/NZS Series High voltage switchgear and control gear AS/NZS 4777 Series Grid connection of energy systems via inverters IEC Utility-interconnected photovoltaic inverters Test procedure of islanding prevention measures NER National Electricity Rules (available at Check this is the latest version before use. Page 2 of 58 Standard STNW1165 Ver 5

8 3. Definitions, Acronyms and Abbreviations 3.1 Definitions For the purposes of this standard, the following definitions apply. Australian Energy Regulator (AER) Connection Applicant Connection Asset Connection Point Customer Customer Asset Distribution System Electricity Distributor/DNSP A Federal Government body responsible for the economic regulation of electricity distribution services in the National Electricity arket. A person who wants to establish or modify connection to the Distribution Network and who makes a connection application as described under the relevant provisions of the NER. Assets that are dedicated to supplying a single customer or group of customers at a single Connection Point. The agreed point of supply established between Ergon Energy and the Proponent. A person who engages in the activity of purchasing electricity supplied through a transmission or distribution system to a connection point; and is registered by AEO as a Customer under Chapter 2. (of the NER). Electrical assets that are owned by the customer and are designed and constructed in accordance with AS/NZS A distribution network, together with the connection assets associated with the distribution network Distribution Network Service Provider. Ergon Energy is the owner, lessor and operator of the electricity distribution network in regional Queensland. Embedded Generating System One or more generating units that are connected directly and operate in parallel with the Distribution Network. Exporting Generating unit Generator Refers to where an Embedded Generating System operates in parallel with the Distribution Network and also exports electricity to the Distribution Network at the connection point. The actual plant capable of generating electricity and all related equipment essential to its function as a single entity. A person who owns, operates or controls a generating system connected to the national grid. Check this is the latest version before use. Page 3 of 58 Standard STNW1165 Ver 5

9 Interconnection Inverter Energy System Synchronous parallel operation of an embedded generating system to the electricity network A system comprising one or more inverters together with one or more energy sources (which may include batteries for energy storage), controls and one or more grid protection devices. Low Voltage Connection Point The low voltage terminals of the distribution transformer. The DNSP is responsible for the operation and maintenance of the transformer and other HV equipment and the Connection Applicant is responsible for the installation, operation and maintenance of the all low voltage equipment. icro Embedded Generating Unit (EGU) ultiple Earth Neutral (EN) Non-parallel Back-up Generation National Electricity arket (NE) Non-export Generation Non-parallel Back-up Generation National Electricity Rules (NER): National etering Identifier (NI) Network: A generating unit as contemplated by AS/NZS As at 1 July 2016, this refers to Inverter Energy Systems with a capability of less than 10 kva for a single phase connection or 30 kva for a three phase connection. ultiple earth neutral system of earthing is one in which the LV neutral conductor is permanently connected to earth. A generating unit which can supply customer load in back-up arrangement which is not connected in parallel and does not synchronise with the distribution network. Loads shall be isolated from the distribution network when being supplied from the nonparallel back-up generating unit. The market that operates in the interconnected national grid. An Embedded Generating System that is paralleled with the distribution network and which does not export electricity into the distribution network. A generating unit which can supply customer load in back-up arrangement which is not connected in parallel and does not synchronise with the distribution network. Loads shall be isolated from the distribution network when being supplied from the nonparallel back-up generating unit. The National Electricity Rules govern the operation of the National Electricity arket. A National etering Identifier as described in NER clause 7.3.1(d). The apparatus, equipment, plant and buildings used to convey, and control the conveyance of, electricity to customers (whether wholesale or retail) excluding any connection assets. In relation to a Network Service Provider, a network owned, operated or controlled by that Network Service Provider. Check this is the latest version before use. Page 4 of 58 Standard STNW1165 Ver 5

10 Network Coupling Point The point at which Connection Assets join the shared Distribution Network. Network Augmentation Works: Augmentation works required on network assets to enable a new project to be supplied or the increase in supply for an existing Connection Applicant. Network Islanded Operation: Generation is allowed to back feed into a portion of the distribution network that is isolated from the rest of the electricity supply network, typically as a result from a protection operation on the transmission or distribution network. Network Non-Exporting: Proponent: QEC Retailer: SCADA Refers to where an Embedded Generating System operates in parallel with the Distribution Network but does not export electricity into the Distribution Network (other than as necessarily required in order to operate in parallel). The relevant owner, operator or controller of the Embedded Generating System (or their agent). Queensland Electricity Connection and etering anual Service and Installation Rules. A person who holds a retailer authorisation under the National Energy Retail Law to sell electricity. Supervisory Control and Data Acquisition this is a system used by Ergon Energy to manage and operate the Distribution Network. 3.2 Acronyms and Abbreviations ACA AEO AEC HV Australian Communications and edia Authority Australian Energy arket Operator Australian Energy arket Commission High Voltage nominally above 1 kv (AC) or 1.5 kv (DC). Check this is the latest version before use. Page 5 of 58 Standard STNW1165 Ver 5

11 4. Network Connection Overview 4.1 Network Connection Agreement The Proponent of any EG installation must enter into an Agreement with Ergon Energy. These Agreements are subject to commercial negotiations between the parties. The Agreement encompasses both the technical and commercial aspects of the connection, addresses the Standards and inimum Technical requirements and specifies the terms and conditions including connection charges, use of system charges and quality of supply in accordance with the NER. The Proponent shall indemnify Ergon Energy and accept liability for safety and supply quality issues that occur when the generating unit is operating. Ergon Energy will provide supply to local customer loads on a no-risk basis. This requirement shall apply to all loads that are connected on the customer side of the network and which can be supplied from the generating unit. 4.2 Connection Assets Ergon Energy separates relevant assets into certain categories based on their location and function. Relevantly: (a) Connection Assets (as the term is used in this anual) can be viewed as including: (i) those components of the Distribution System that are used to provide Connection Services (usually being dedicated to a single Connection Customer or group of such customers); and (ii) any dedicated assets constructed by a ajor Customer for the purposes of the connection (Customer Connection Assets); (b) the Connection Point is the agreed point of supply to a customer, and hence is the physical point at which Ergon Energy s Connection Assets meet the Customer s Connection Assets. Ideally the Connection Point should be located as close as possible to the Network Coupling Point (see below). Note that assets upstream of the Connection Point will ultimately be owned and operated by Ergon Energy, and conversely, assets downstream of the Connection Point will generally be owned and operated by the Customer; and (c) the Network Coupling Point is the point determined by Ergon Energy at which Ergon Energy s Connection Assets meet the shared Distribution Network (that is, the boundary between assets providing dedicated services (Connection Assets) and assets providing shared services (Shared Network Assets). When determining the Network Coupling Point, Ergon Energy will take into account the current status of the Distribution System, existing Connection Applications and Ergon Energy s strategic plans out to the nominated planning horizon. (d) the Distribution Network comprises the assets that provide services to multiple Connection Customers; (e) Customer Assets comprise the Customer s assets located downstream of the Connection Point; and (f) the etering Point is the point located as close as possible to the Connection Point at which the metering installation measures the throughput of electricity. The diagram below illustrates some examples of these points. Table 1 of Appendix 2 of the ajor Customer Connection anual also illustrates these in respect of various common network configurations. Check this is the latest version before use. Page 6 of 58 Standard STNW1165 Ver 5

12 Network (HV) Legend NCP Network Coupling Point CP Connection Point P etering Point NCP NCP NCP P CP Connection Assets HV Connection Assets HV & LV Customer Owned Connection Assets HV P CP Customers Electrical Installation Customer Facility or Development Site Customer 1 CP P Customers Electrical Installation Customer Facility or Development Site Customer 2 Customers Electrical Installation Customer Facility or Development Site Customer 3 Figure 1 Asset Boundary Principles Any services provided by means of, or in connection with, Ergon Energy s Distribution System are classified as distribution services under the NER. The classification of the service being provided and the method of cost recovery will be in line with Ergon Energy s AER approved Distribution Determination and Pricing Proposal. 4.3 Technical Considerations The following items must be addressed for all connections of EG within the distribution network: Network Safety and Security; Network and Interconnection Protection; Network Infrastructure Thermal Capacity; Network Voltage Control; Generating unit Fault Level Contribution; Generating unit Operating Power Factor; Quality of Supply Generated; Network Stability; and Operations. Prior to the connection of an embedded generating system to the distribution network Ergon Energy will carry out a study of the network. The study and subsequent report (technical assessment) will identify any technical requirements for the proposed connection between the Generator and Ergon Energy. Check this is the latest version before use. Page 7 of 58 Standard STNW1165 Ver 5

13 Ergon Energy will require information (as detailed later in the document) to perform the study, fees may apply. 4.4 Types of Embedded Generating Systems For the purpose of this Standard, all proposed generating units designed to connect to the distribution network as either export or non-export embedded generating as shown in Table 1. Operation Type Export Non-export Stand-by generating unit with testing Yes Yes requirements (typically 6 hours per 3 months) Bumpless or seamless load transfer between No Yes generating unit and network (short time parallel operation typically less than 1 minute) Commercial generating unit operation including Yes Yes co-generation and tri-generation Table 1 Types of Embedded Generating Systems Export Embedded Generation An export embedded generating unit is an embedded generating unit designed to export electricity that is in excess to the site load (Demand) to the distribution network. A direct connected generation unit is directly connected to the distribution system. All export embedded generating units may require communication links installed between Ergon Energy and the embedded generating unit installation to provide SCADA monitoring and control. This will be determined by Ergon Energy in accordance with Section Non-Export Embedded Generation A non-export embedded generating unit is an embedded generating unit within a Customer s installation which does not exceed the Customer s electricity demand. Where the Embedded Generating System and does not have an agreement to export electricity to the distribution network, reverse power flow protection (towards the network) must be installed to disconnect the embedded generating unit from the distribution network in the event that the minimum import electricity buffer is encroached upon. 4.5 Permissible Generating Unit Connection Arrangements Typical connection arrangements for embedded generating systems are given in Annex A for both rotating generating plant and inverter based systems. There are a number of configurations of HV and LV embedded generating system arrangements involving the network connection point, network coupling point, generating unit location and customer load. To minimise the potential for adverse impact on the quality of electricity supply to other network customers, the following limitations shall apply for this connection arrangement: Ergon Energy will not provide LV circuit ties between the dedicated transformer / LV circuit incorporating the EG network connection point and adjacent transformers or substations. Only local load associated with the Proponent s own installation shall be supplied from the section of the customer s installation that is supplied from the EG. The connection of other customer loads to the dedicated substation or transformer as applicable shall not be permitted. Where this results in a requirement for additional network equipment or Check this is the latest version before use. Page 8 of 58 Standard STNW1165 Ver 5

14 infrastructure, the total cost of such equipment/infrastructure shall be borne by the Proponent. If the embedded LV generation facility is proposed to connect to the Ergon Energy distribution network at an existing transformer or substation, any existing loads not related to the local customer site must be relocated to other network supply sources or an approved protection system installed. The total cost of such works shall be borne by the Proponent. Notwithstanding the above limitations, connection to, and parallel operation with, any part of Ergon Energy s network shall be subject to achieving compliance with the requirements outlined in this document at each point capable of paralleling the generating unit with Ergon Energy s LV distribution network. Furthermore, in accordance with this document and Qld Electricity Connections and etering anual - Service and Installation Rules, the Proponent shall ensure that where an embedded LV generating unit connects within the customer s installation and supplies only part of the customer s installation: Adequate mechanisms are provided to ensure that paralleling of Ergon Energy substation transformers from within the customer s installation cannot occur; and/or The EG cannot be connected to the Ergon Energy LV distribution network without synchronisation and the associated protection systems. 5. Connection Enquiry and Application Process Regardless of whether the Embedded Generating System will be an Exporting Embedded Generating System or a Non-Exporting Embedded Generating System, the connection of the Embedded Generating System first requires Ergon Energy s consent to interconnect. A Proponent wishing to submit a formal connection enquiry or connection application for either a Non-Exporting Embedded Generating System or Exporting Embedded Generation System must do so using Ergon Energy s approved forms. The relevant process and forms are set out at: in the Large Scale Renewables and Generation section. 6. Technical Requirements and Performance Standards 6.1 General Connection Applicants, facilities, Generators and EG shall comply with the relevant technical requirement applicable to their generating unit, any applicable performance standards as defined in the NER and Ergon Energy s Connection Agreement. The equipment associated with each generating unit must be designed to withstand without damage the range of operating conditions which may arise. Check this is the latest version before use. Page 9 of 58 Standard STNW1165 Ver 5

15 6.2 Network Connection Arrangement and Voltage Level General Unless otherwise specified by Ergon Energy, a Generator is required to connect to Ergon Energy s network via a single point of connection at a voltage agreed with Ergon Energy. It is the Generator s responsibility to provide a circuit breaker at the point of connection, generating unit transformer(s) and all associated protection controls and ancillary equipment Nominal Interconnection Voltage Ergon Energy distribution networks normally include systems operating at 132 kv, 110 kv, 66 kv, 33 kv, 22 kv, 11 kv and 415 V. The nominal supply voltage for the low voltage network is 240 Volts, phase to neutral, and 415 Volts phase to phase with a tolerance of 6%. Grid connected inverters and grid protection devices shall be capable of operation within these parameters. The voltage level which an EG will be connected depends primarily on the size of the generating unit, and the availability of distribution network in the area concerned. An investigation will need to be undertaken by Ergon Energy to determine the most appropriate connection voltage Power Frequency The performance standard for power frequency variations are defined by the National Electricity Rules and the Frequency Operating Standards published by the AEC 1. These standards cover normal conditions as well as the period immediately following critical events when frequency may be disturbed. The AEC standards state that The frequency operating standards require that, during periods when there are no contingency events or load events, the frequency be maintained within the normal operating frequency band (49.85 Hz to Hz) for 99% of the time, with larger deviations permitted within the normal operating frequency excursion band (49.75 Hz to Hz) for no more than 1% of the time. (See Table 2) 1 AS/NZS details that the frequency range is typically plus or minus 1 Hz, but it is usually much less where synchronous interconnection is used on a continental scale. This requirement is overridden by the National Electricity Rules. Check this is the latest version before use. Page 10 of 58 Standard STNW1165 Ver 5

16 Condition Containment Stabilisation Recovery Accumulated time error 5 seconds No contingency to Hz*, to Hz within 5 minutes event or load event to Hz 99% of the time^ Generation event or load event 49.5 to 50.5 Hz to Hz within 5 minutes Network event 49 to 51 Hz 49.5 to 50.5 Hz within 1 minute to Hz within 5 minutes Separation 49 to 51 Hz 49.5 to 50.5 Hz to Hz event ultiple contingency event within 2 minutes 47 to 52 Hz 49.5 to 50.5 Hz within 2 minutes ^ - This is known as the normal operating frequency band. * - This is known as the normal operating frequency excursion band. Table 2 Frequency Standard (Except islands) 2 within 10 minutes to Hz within 10 minutes The frequency standards in Table 3 apply to where a part of the national grid becomes islanded. This table does not strictly apply to isolated systems but will be used by Ergon Energy as no other standard applies at this time. Condition Containment Stabilisation Recovery No contingency event or load event 49.5 to 50.5 Hz Generation event, 49 to 51 Hz 49.5 to 50.5 Hz within 5 minutes load event or network event The separation event that formed the island 49.0 to 51.0 Hz within 2 minutes ultiple contingency event including a further separation event 49 to 51 Hz or a wider band notified to NECO by a relevant Jurisdictional Coordinator 47 to 52 Hz 49.0 to 51.0 Hz within 2 minutes Table 3 Frequency Standard for National Grid - Island Conditions to 50.5 Hz within 10 minutes 49.5 to 50.5 Hz within 10 minutes Network Characteristics Depending on the location of the proposed connection Ergon Energy Network is operated as a solidly or impedance earthed system. 2 Frequency Operating Standards published by the AEC Reliability Panel Frequency Operating Standards Determination Sept 2001 Part A Summary of Standards. 3 Frequency Operating Standards published by the AEC Reliability Panel Frequency Operating Standards Determination Sept 2001 Part A Summary of Standards. Check this is the latest version before use. Page 11 of 58 Standard STNW1165 Ver 5

17 6.2.5 Equipment Ratings The equipment ratings on the Ergon Energy or customer networks shall not be exceeded when the generation units are in parallel operation. Ergon Energy will make available existing fault levels and equipment ratings on a project by project basis. Proponents shall provide a fault level study to Ergon Energy to demonstrate compliance Fault Levels and Protection Impacts In designing protection associated with EG interconnection, faults and abnormalities to be considered will be: In the generating unit itself In the EG customer installation In the interconnection assets In the wider utility network Typical distribution feeders are fed radially from a utility substation. In these feeders, all of the short-circuit fault current for faults on the feeder, as well as the load current, will come from the source substation. The magnitude of the fault current is determined by the impedances of the utility source, the transformers, reactors and feeder conductors etc, and fault resistance. Embedded synchronous generating units, will increase the fault current level at the fault point and reduce the current being supplied by the source substation to the point of actually causing a reversal of fault current flow in some circuits. The maximum and minimum values of fault current are an important consideration for any protection scheme. aximum values determine the interrupting rating needed for circuit breakers, automatic circuit reclosers (ACRs), fuses, etc as well as the upper design limit for the protection scheme performance. inimum current values determine the lower limit settings of overcurrent, earth fault relays and other protective devices to provide a satisfactorily high probability of detecting all faults. On a radial feeder, all protective devices between the substation and the fault measure the same current as the substation is the only source. This simplifies the coordination of overcurrent tripping devices to interrupt the fewest number of customers. Earth fault coordination may be affected if feeders have other sources of earth current. Sources of feeder fault current due to EG may affect relay, fuse and ACR coordination, equipment rating, and safety of utility personnel and the general public. The magnitude of fault current from these sources will depend upon the type, size, and number of generating units, their impedances, and their location with respect to the fault and utility substation. If the EG contribution is large, the operation of the relays at the substation may be delayed due to a reduction in fault current from the source substation. A more likely case is that of a relatively high impedance EG source located near the source substation. Such an arrangement contributes limited fault current until the utility circuit breaker opens, which may result in slow detection and sequential clearing of the fault. These multiple current source problems will apply to phase-toearth faults if there is an earthed neutral (transformer or generating unit) at the faulted network voltage level. A fault study is essential for EG proposals covering faults in the customer installation and the utility network. This should recognise the presence of other EG installations that may be electrically nearby. Check this is the latest version before use. Page 12 of 58 Standard STNW1165 Ver 5

18 The fault levels shall not exceed the generating unit equipment rating. Temporary prospective fault levels (less than 1 minute) above the equipment rating may be tolerable based on a case by case risk assessment basis. Where transformers operate in parallel, Ergon Energy has additional requirements as given in Annex D. Lightning Insulation Levels For Surge Arresters Surge arresters shall as a minimum be installed at the HV connection point. The minimum insulation levels for the surge arresters are given in Table 4. Network Voltage Lightning Impulse Withstand Voltage (kv) (kv) Table 4 Lightning Impulse Withstand Voltage for Surge Arresters 6.3 Control System for Embedded Generating System General Requirements The Proponent must ensure that each point capable of paralleling the generating unit to the network contains suitable protection and control as detailed in this standard eans of Isolation The Proponent must provide a means of isolation, capable of disconnecting the whole of the customer s electrical system from the network, and vice versa. This means of isolation must be lockable, in the open position only, by a separate padlock Synchronising and Synchronising Check Facilities The Proponent must supply synchronising and synchronising check facilities at the Generator s circuit breaker that interfaces with the network and where ever else they may choose to synchronise. These facilities are to include a dead bus check system preventing the customer closing the generating unit onto the network when it is de-energised. Note: Ergon Energy circuit breakers are not fitted with synchronising facilities Generating System Control The Proponent must be fitted with either automatic or operator controlled equipment, which ensures that frequencies, voltage, and phase sequences are identical before connection to the network. In addition, the equipment must ensure that after a disconnection there is no chance of re-closing onto the network before synchronising is completed. To ensure control over real and reactive power contribution to the network, adequate control must be provided over both the governor (regarding input motive power to the rotor) and the excitation system (controlling output voltage level). The generating unit kw and kvar output must be controlled within the agreed limits. Power factor limits are given in Section 0. Check this is the latest version before use. Page 13 of 58 Standard STNW1165 Ver 5

19 6.3.5 Reactive Power Generators must be capable of injecting or absorbing VArs in accordance with the requirements of the NER and Ergon Energy may need to impose limits on, or specify the operating power factor to ensure there are no excessive voltage swings to customers Fault Level Control The Proponent has the potential raise the fault levels of the network beyond the capacity of Ergon Energy interruption devices. This must be determined at the design stage. The Generator will bear the costs that Ergon Energy may incur in respect of fault level control Feeder Rating The Proponent has the potential to increase the load flow of the network beyond its capacity. This must be determined at the design stage. The Generator will bear the costs that Ergon Energy may incur in respect of feeder capacity augmentation to facilitate the network connection of the EG Feeder Reclosing Ergon Energy applies an automatic feeder re-closing scheme on most of its distribution feeders. Automatic re-energisation of the feeder will occur at a time three to five seconds after the feeder has been disconnected due to a system disturbance. The customer control and protection scheme shall be designed to ensure that the generating unit has disconnected within three seconds of the loss of supply. Failure of the customer s equipment to disconnect during an Ergon Energy loss of supply may result in damage to the generating equipment Reconnection An EG is required to disconnect to ensure that a faulted section of network is effectively deenergised after a power system fault or operator switching action. When the system voltage has been restored to the network side of the generating unit connection point, and the voltage maintained within protection limits for a period of greater than 60 seconds, the generating unit may reconnect. 6.4 Protection System General A general discussion on the protection considerations associated with the connection and parallel operation of synchronous generating units and inverter energy systems with the distribution network is given in Annexes D, E & F respectively. All protection equipment must comply with the relevant Australian and International Standards. All protection equipment must be tested and commissioned by a competent commissioning officer, to the agreed settings, and a Certificate of Compliance for the complete generating unit installation must be issued by the Proponent to Ergon Energy prior to connection to the network. The Proponent must keep a written record of all protection settings and of test results. A copy of this record should be available at the service point or as required by Ergon Energy. The protection shall be designed in accordance with Ergon Energy standards, which require a main and back-up set of protection to detect all credible fault types. The protection will include sufficient redundancy to ensure that a faulted element within the protection zone is disconnected from the network within the applicable fault clearance time with any single protection element (including communications upon which that protection system depends) out of service. Check this is the latest version before use. Page 14 of 58 Standard STNW1165 Ver 5

20 The Generator must submit complete details of the generating unit protection system including the proposed settings to Ergon Energy for review and agreement. EGs must not be able to operate in network islanded mode. To prevent the generating unit operating in network island mode, an Ergon Energy approved protection scheme/s shall be installed. These schemes may include: An inter-trip protection scheme (DIT) Voltage vector shift (VS) Rate of Change of Frequency (ROCOF) protection Reverse power protection Overvoltage/Undervoltage (OV/UV) Overfrequency/Underfrequency (OF/UF) Loss of ains (Lo) The customer s EG unit shall disconnect from the Network in the event of a fault on the Ergon Energy HV and LV network. Approved protection shall be provided to ensure this occurs. These schemes may include: An inter-trip protection scheme Voltage vector shift (VS) Rate of Change of Frequency (ROCOF) protection Neutral voltage displacement Negative sequence voltage or current Overcurrent and earth fault Directional overcurrent and earth fault Overvoltage/Undervoltage Overfrequency/Underfrequency Loss of ains (Lo) Proponents may propose other forms of loss of mains protection schemes which are commercially available. These schemes need to be approved by Ergon Energy. In addition to the protection installed for the generating unit, the Generator Proponent must install a protection system so that: The EG cannot connect onto the Ergon Energy Network unless all phases of the Network are energised at the supply point. The connection must ensure synchronisation before closure. If one or more phases of the Network are lost, then the EG must disconnect from the Network; The protective equipment is operating within the agreed protection settings; If a system abnormality occurs that results in an unacceptable deviation of voltage or frequency at the supply point, the EG must be disconnected from the Network; and The EG is to automatically disconnect from the Network in the event of failure of any auxiliary supplies to the protection equipment that would inhibit its correct operation. When any of these conditions are detected the EG must be disconnected from the network at an agreed circuit breaker within the EG that will ensure complete disconnection. To detect these conditions, as set out above, the Proponent must install suitable protection. Check this is the latest version before use. Page 15 of 58 Standard STNW1165 Ver 5

21 The protection equipment shall be compliant with the relevant sections of IEC and operate the circuit breaker directly or through interposing equipment that is also compliant to the relevant sections of IEC arshalling of protection trips through control equipment that is not compliant to IEC is not acceptable. The instrument transformers used to interface the protection equipment to the proponents installation must be compliant with the relevant sections of AS Types of Protection Loss of ains (Lo) The generating unit must be disconnected from the distribution network whenever the network is intended to be de-energised. This includes any operation of Ergon Energy s substation circuit breaker and / or re-closer controlling the feeder components that supplies the EG. Operation for either a fault or routine switching operation requires the EG to disconnect from the network. A communication link may be required between the EG and the Ergon Energy s substation. This link must be continuously monitored for integrity. In the event that the link fails the EG must be automatically disconnected from the network until the communications link is restored Synchronising Facilities The generating unit control system must include synchronising facilities at the circuit breaker that interfaces with the network and / or where ever else that it is proposed to synchronise the generating unit with the network Under/Over Frequency Under and over frequency protection must be installed at the connection point and/or at the generating unit location. The frequency protection tripping will be based on the proposed network connection arrangement and operating requirements. The protection frequency settings will be determined at the design stage (based on Table 2) and subject to the results of the network study and subsequent Engineering Report Under/Over Voltage Under and over voltage protection must be installed to monitor all three phases at the connection point. This protection is set to detect if the phase to neutral voltage on any phase at this point exceeds predetermined values, which will be based on the proposed network connection arrangement and operating requirements. The over/under voltage protection settings will be determined at the design stage and subject to the results of the network study and subsequent Engineering Report Negative sequence voltage & current protection Negative sequence voltage and current protection shall be installed at the generating unit to protect against voltage and current imbalance from the generating unit source, which together with neutral voltage displacement (NVD) protection also provides back-up protection to the Loss of ains protection Overcurrent and earth fault protection Overcurrent and earth fault protection shall also be provided at the generating unit and this shall provide back-up to the protection installed at the network connection point. This protection shall be set to detect faults within the customer s installation and Ergon Energy s distribution network (back- Check this is the latest version before use. Page 16 of 58 Standard STNW1165 Ver 5

22 up to the network connection CB OCEF protection). This protection must coordinate with Ergon Energy s network protection scheme. Generating unit overcurrent and earth fault protection relays should have compensation for under voltage field weakening unless the Proponent can demonstrate that voltage depression at the generating unit during fault events will not adversely impact on protection scheme operation Neutral Displacement protection Where the export of power is intended, Neutral Displacement (NVD) protection may be required. Neutral voltage displacement protection is required to ensure disconnection of a generating unit in the event of a high voltage network earth fault. This backfeed situation arises because of the delta to star connection of the distribution transformers. As this protection scheme will require the installation of voltage transformer(s) on the Ergon Energy HV distribution network near the network connection point; the voltage transformer(s) will be supplied and installed by Ergon Energy. The total cost of this VT and associated equipment will be borne by the Proponent. The voltage transformer(s) required for this protection scheme may be either 3 x single phase voltage transformers or a single three phase 5 limb voltage transformer, with the primary winding star point connected to earth and the secondary winding supplying a NVD protection relay. If and independent Overvoltage/Undervoltage or Overfrequency/Underfrequency protection is required, an additional star connected secondary winding may be provided on the voltage transformer. Ergon Energy will provide the VT secondary wiring to the Generating Unit Interface Cubicle. The Proponent will be required to supply and install the NVD protection relay and associated equipment / wiring within the EG facility. Special requirements exist for inverter energy systems. Annex E specifies alternative protection for generation with ratings between 30 kva and 200 kva, and Annex F specifies alternative protection for generation connected at low voltage with ratings greater than 200 kva Reverse power / power limit protection Reverse power (with respect to sending electricity back to the distribution network), or power limit protection shall be installed at the network connection point, where the export of power has not been approved by Ergon Energy. Similarly, where Ergon Energy has nominated a limit on the amount of power that can be exported to the distribution network as a result of network infrastructure or performance constraints power limit protection shall be installed at the network connection point. Any power limit protection settings will be determined by Ergon Energy at the detailed design stage after the detailed network studies have been undertaken. The power protection must include three phase power monitoring relays installed at the Network Coupling Point to prevent the embedded generating unit exporting power beyond the agreed power limit to the distribution network. Where no export operation is permitted the power monitoring protection is to be set to ensure electricity is always imported from the distribution network; (typically a minimum threshold of 10% of the nominal supply rating to the customer s installation as determined by instrument transformer and protection relay capabilities). Check this is the latest version before use. Page 17 of 58 Standard STNW1165 Ver 5

23 Where an export power limit has been provided by Ergon Energy the Proponent shall have a protection system that is capable of operating within 10% of the nominated power limit. Whenever the power protection limit is exceeded for more than 2 seconds, the embedded generating unit (or portions of the generating plant) must be disconnected from the distribution network so as to maintain a value within the agreed operating threshold. Power protection shall be compliant with the relevant sections of IEC60255 and directly operate the circuit breaker or operate through interposing equipment that is also compliant to the relevant sections of IEC In addition to the power protection specified by Ergon Energy the user may manage their power export through their control system. The instrument transformers used to interface the protection relaying equipment to the proponents installation shall be compliant with the relevant sections of AS Rate of Change of Frequency (ROCOF) The ROCOF relay controls the disconnection of a EG from the network by monitoring frequency excursions. It is specifically designed to protect the network from the potential damaging effects of reconnection whilst out of synchronism Remote or Transfer Trip (Intertripping) Where a protection signalling communications link exists, or can be included within the scope of an EG project, then remote tripping from Ergon Energy to the EG installation can provide: a) Interruption of the EG fault current flow or energisation of all faults on the interconnecting feeder detected by protection at the source substation. b) Secure, quick and direct separation at the EG installation for Lo conditions. This can include manual or auto tripping all of the circuit breakers in the source substations that could result in islanding. The communications link can also be used for monitoring or SCADA type services from the EG installation back to Ergon Energy. Where such a communications link is a part of the primary protection scheme either for interconnecting circuit protection or Lo, then its availability and integrity should be monitored. Depending on the level of risk accepted, it may be necessary to prevent operation of the EG, but not customer load, or not allow parallel operation of the generation, should the communications link be out of service. Suitable communications link include: Protection signalling quality digital radio Optical fibre cable GS modem or mobile phone communication links are not considered to be a protection signalling quality but may be suitable for SCADA. The most cost effective communication link will be dependent on the distance between the generation facility and the Ergon Energy substation. The longer distance generally favours the digital radio link. Check this is the latest version before use. Page 18 of 58 Standard STNW1165 Ver 5