CSC-121 Breaker Protection IED Technical Application Manual

Transcription

1 CSC-121 Breaker Protection IED Technical Application Manual

2 Version:V1.01 Doc. Code: 0SF (E) Issued Date: Copyright owner: Beijing Sifang Automation Co., Ltd Note: the company keeps the right to perfect the instruction. If equipments do not agree with the instruction at anywhere, please contact our company in time. We will provide you with corresponding service. is registered trademark of Beijing Sifang Automation Co., Ltd. We reserve all rights to this document, even in the event that a patent is issued and a different commercial proprietary right is registered. Improper use, in particular reproduction and dissemination to third parties, is not permitted. This document has been carefully checked. If the user nevertheless detects any errors, he is asked to notify us as soon as possible. The data contained in this manual is intended solely for the IED description and is not to be deemed to be a statement of guaranteed properties. In the interests of our customers, we constantly seek to ensure that our products are developed to the latest technological standards as a result it is possible that there may be some differences between the hardware/software product and this information product. Manufacturer: Beijing Sifang Automation Co., Ltd. Tel: , ext Fax: sf_sales@sf-auto.com Website: Add: No.9, Shangdi 4th Street, Haidian District, Beijing, P.R.C

3 Preface Purpose of this manual This manual describes the functions, operation, installation, and placing into service of IED CSC-121. In particular, one will find: Information on how to configure the IED scope and a description of the IED functions and setting options; Instructions for mounting and commissioning; Compilation of the technical specifications; A compilation of the most significant data for experienced users in the Appendix. Target Audience Protection engineers, commissioning engineers, personnel concerned with adjustment, checking, and service of selective protective equipment, automatic and control facilities, and personnel of electrical facilities and power plants. Applicability of this Manual This manual is valid for SIFANG Breaker Protection IED CSC-121; firmware version V1.00 and higher Indication of Conformity Additional Support In case of further questions concerning IED CSC-121 system, please contact SIFANG representative. Safety information Strictly follow the company and international safety regulations. Working in a high voltage environment requires serious approch to aviod human injuries and damage to equipment

4 Do not touch any circuitry during operation. Potentially lethal voltages and currents are present Avoid to touching the circuitry when covers are removed. The IED contains electirc circuits which can be damaged if exposed to static electricity. Lethal high voltage circuits are also exposed when covers are removed Using the isolated test pins when measuring signals in open circuitry. Potentially lethal voltages and currents are present Never connect or disconnect wire and/or connector to or from IED during normal operation. Dangerous voltages and currents are present. Operation may be interrupted and IED and measuring circuitry may be damaged Always connect the IED to protective earth regardless of the operating conditions. Operating the IED without proper earthing may damage both IED and measuring circuitry and may cause injuries in case of an accident. Do not disconnect the secondary connection of current transformer without short-circuiting the transformer s secondary winding. Operating a current transformer with the secondary winding open will cause a high voltage that may damage the transformer and may cause injuries to humans. Do not remove the screw from a powered IED or from an IED connected to power circuitry. Potentially lethal voltages and currents are present Using the certified conductive bags to transport PCBs (modules). Handling modules with a conductive wrist strap connected to protective earth and on an antistatic surface. Electrostatic discharge may cause damage to the module due to electronic circuits are sensitive to this phenomenon 4

5 Do not connect live wires to the IED, internal circuitry may be damaged When replacing modules using a conductive wrist strap connected to protective earth. Electrostatic discharge may damage the modules and IED circuitry When installing and commissioning, take care to avoid electrical shock if accessing wiring and connection IEDs Changing the setting value group will inevitably change the IEDs operation. Be careful and check regulations before making the change

6 Contents Chapter 1 Introduction Overview Features Functions Protection functions Monitoring functions Station communication IED software tools... 6 Chapter 2 General IED application Display information LCD screen display function Analog display function Report display function Menu dispaly function Report record Disturbance recorder Introduction Setting Self supervision function Introduction Self supervision principle Self supervision report Time synchronization Introduction Synchronization principle Synchronization from IRIG Synchronization via PPS or PPM Synchronization via SNTP Setting Introduction Operation principle Authorization Introduction Chapter 3 Overcurrent protection Overcurrent protection Introduction Protection principle Time characteristic Inrush restraint feature Direciton determination feature Logic diagram Input and output signals

7 1.4 Setting parameters Setting list Reports Technical data Chapter 4 Earth fault protection Earth fault protection Introduction Protection principle Time characteristic Inrush restraint feature Direction determination feature Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 5 Neutral earth fault protection Neutral earth fault protection Introduction Protection principle Time characteristic Inrush restraint feature Direction determination Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 6 Sensitive earth fault protection Sensitive earth fault protection Introduction Protection principle Time characteristic Direction determination feature Logic diagram Input and output signals Setting parameters Setting list IED report Technical data Chapter 7 Negative sequence overcurrent protection Negative sequence overcurrent protection... 68

8 1.1 Introduction Protection principle Protection function description Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 8 Thermal overload protection Thermal overload protection Introduction Function principle Function description Input and output signals Setting parameters Setting lists Reports Technical data Chapter 9 Overload protection Overload protection Protection principle Function description Logic diagram Input and output signals Setting parameters Setting lists Reports Chapter 10 Overvoltage protection Overvoltage protection Introduction Protection principle Phase to phase overvoltage protection Phase to earth overvlotage protection Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 11 Undervoltage protection Undervoltage protection Introduction Protection principle

9 1.2.1 Phase to phase underovltage protection Phase to earth undervoltage protection Depending on the VT location Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 12 Displacement voltage protection Displacement voltage protection Introduction Protection principle Function description Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 13 Circuit breaker failure protection Circuit breaker failure protection Introduction Function Description Current criterion evaluation Circuit breaker auxiliary contact evaluation Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 14 Dead zone protection Dead zone protection Introduction Protection principle Function description Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 15 STUB protection

10 1 STUB protection Introduction Protection principle Function description Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 16 Poles discordance protection Poles discordance protection Introdcution Protection principle Function description Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 17 Synchro-check and energizing check function Synchro-check and energizing check function Introduction Function principle Synchro-check mode Energizing check mode Override mode Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 18 Auto-reclosing function Auto- reclosing Introduction Function principle Single-shot reclosing Multi-shot reclosing AR coordination between tie CB and side CB Auto-reclosing operation mode Auto-reclosing initiation Cooperating with external protection IED

11 1.2.7 Auto-reclosing logic AR blocked conditions Logic diagram Input and output signals Setting parameters Setting lists Reports Technical data Chapter 19 Secondary system supervision Current circuit supervision Function description Input and output signals Setting parameters Setting lists Reports Fuse failure supervision Introduction Function principle Three phases (symmetrical) VT Fail Single/two phases (asymmetrical) VT Fail Logic diagram Input and output signals Setting parameters Setting list Reports Technical data Chapter 20 Monitoring Synchro-check reference voltage supervision Check auxiliary contact of circuit breaker Chapter 21 Station communication Overview Protocol IEC communication protocol IEC communication protocol Communication port Front communication port RS485 communication ports Ethernet communication ports Technical data Typical substation communication scheme Typical time synchronizing scheme Chapter 22 Hardware Introduction IED structure

12 1.2 IED module arrangement Local human-machine interface Introduction Liquid crystal display (LCD) LED Keyboard IED menu Menu construction Operation status Reports search Set time Contrast Settings IED setting Test binary output Testing operation Analog input module Introduction Terminals of analog input module Technical data Communication module Introduction Terminals of Communication module Substaion communication port RS232 communication ports RS485 communication ports Ethernet communication ports Time synchronization port Technical data Binary input module Introduction Terminals of Binary Input Module Technical data Binary output module Introduction Terminals of Binary Output Module Technical data Power supply module Introduction Terminals of Power Supply Module Technical data Techinical data Type tests Product safety-related tests

13 8.1.2 Electromagnetic immunity tests DC voltage interruption test Electromagnetic emission test Mechanical tests Climatic tests CE Certificate IED design Chapter 23 Appendix General setting list Function setting list Binary setting list General report list Typical connection Time inverse characteristic kinds of IEC and ANSI inverse time characteristic curves User defined characteristic Typical inverse curves CT requirement Overview Current transformer classification Abbreviations (according to IEC , -6, as defined) General current transformer requirements Protective checking current CT class Accuracy class Ratio of CT Rated secondary current Secondary burden Rated equivalent secondary e.m.f requirements Line differential protection Transformer differential protection Busbar differential protection Distance protection Definite time overcurrent protection and earth fault protection Inverse time overcurrent protection and earth fault protection

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15 Chapter 1 Introduction Chapter 1 Introduction About this chapter This chapter gives an overview of SIFANG Breaker Protection IED CSC

16 Chapter 1 Introduction 1 Overview The CSC-121 is selective, reliable and high speed breaker management and backup protection IED (Intelligent Electronic Device), which is used as backup protection cooperating with main protection in different applications such as overhead line, cable, transformer, reactor and busbar protection. It can also work as a dedicated breaker management relay for circuit breaker. The IED has powerful capabilities to cover following applications: Used in a wide range of voltage levels, up to 1000kV Applied to overhead lines and cables, as backup protection IED Applicable in subtransmission network and distribution network Applied to transformer as backup protection IED Breaker management protection for any substation arrangement such as one and half breakers arrangement, double bus arrangement, etc. Work as a dedicated breaker protection for single circuit breaker Suitable for single pole/three poles tripping and closing conditions Communication with station automation system The IED provides a completely protection functions library, including current protection, voltage protection, auto-reclosing, breaker failure protection, thermal overload protection, etc., to cover most of the requirements of different applications. 2

17 Chapter 1 Introduction 2 Features Protection and monitoring IED with extensive functional library, user configuration possibility and expandable hardware design to meet with user s special requirements A complete protection functions library, include: Overcurrent protection (50, 51, 67) Earth fault protection (50N, 51N, 67N) Neutral earth fault protection (50G, 51G, 67G) Sensitive earth fault protection (50Ns, 51Ns, 67Ns) Negative-sequence overcurrent protection (46) Thermal overload protection (49) Overload protection (50OL) Overvoltage protection (59) Undervoltage protection (27) Displacement voltage protection (64) Circuit breaker failure protection (50BF) Poles discordance protection (50PD) Dead zone protection (50SH-Z) STUB protection (50STUB) Synchro-check and energizing check (25) Auto-recloser function for single- and/or three-phase reclosing (79) Voltage transformer secondary circuit supervision (97FF) Current transformer secondary circuit supervision Self-supervision to all modules in the IED Complete information recording: tripping reports, alarm reports, startup reports and general operation records. Any kind of reports can be stored up to 2000 and be memorized in case of power disconnection Up to three electric/optical Ethernet ports can be selected to communicate with substation automation system by IEC61850 or IEC protocols Up to two electric RS-485 ports can be selected to communicate with 3

18 Chapter 1 Introduction substation automation system by IEC protocol Time synchronization via network(sntp), pulse and IRIG-B mode Configurable LEDs (Light Emitting Diodes) and output relays satisfied users requirement Versatile human-machine interface Multifunctional software tool CSmart for setting, monitoring, fault recording analysis, configuration, etc. 4

19 Chapter 1 Introduction 3 Functions 3.1 Protection functions Description ANSI Code IEC Logical Node Name IEC graphical symbol Current protection Overcurrent protection 50,51,67 PTOC Earth fault protection 50N, 51N, 67N PEFM 3I INV > 3I >> 3I >>> I 0INV > I 0 >> I 0 >>> Neutral earth fault protection Sensitive earth fault protection Negative-sequence overcurrent protection 50G, 51G, 67G 50Ns, 51Ns, 67Ns 46 3I NE > 3I NE >> Thermal overload protection 49 PTTR Ith Overload protection 50OL PTOC 3I >OL Voltage protection Overvoltage protection 59 PTOV Undervoltage protection 27 PTUV 3U> 3U>> 3U< 3U<< Displacement voltage protection 64 V E > Breaker control function Breaker failure protection 50BF RBRF 3I> BF I 0 >BF I 2 >BF Dead zone protection 50SH-Z STUB protection 50STUB PTOC 3I>STUB Poles discordance protection 50PD RPLD 3I< PD I 0 >PD I 2 >PD Synchro-check and energizing check 25 RSYN Auto-recloser 79 RREC O I 5

20 Chapter 1 Introduction Description ANSI Code IEC Logical Node Name Single- and/or three-pole tripping 94-1/3 PTRC IEC graphical symbol CT secondary circuit supervision Secondary system supervision VT secondary circuit supervision 97FF 3.2 Monitoring functions Description Synchro-check reference voltage supervision Auxiliary contacts of circuit breaker supervision Self-supervision Fault recorder 3.3 Station communication Description Front communication port Isolated RS232 port Rear communication port 0-2 isolated electrical RS485 communication ports 0-3 Ethernet electrical/optical communication ports Time synchronization port Communication protocols IEC protocol IEC protocol 3.4 IED software tools Functions 6

21 Chapter 1 Introduction Functions Reading measuring value Reading IED report Setting IED testing Disturbance recording analysis IED configuration Printing 7

22 Chapter 1 Introduction 8

23 Chapter 2 General IED application Chapter 2 General IED application About this chapter This chapter describes the use of the included software functions in the IED. The chapter discusses general application possibilities. 9

24 Chapter 2 General IED application 1 Display information 1.1 LCD screen display function The LCD screen displays measured analog, report ouputs and menu. 1.2 Analog display function The analog display includes measured Ia, Ib, Ic, 3I0, I5, Ua, Ub, Uc, U4 1.3 Report display function The report display includes tripping, alarm and operation recording. 1.4 Menu dispaly function The menu dispaly includes main menu and debugging menu, see chapter Chapter 22 for detail. 10

25 2 Report record Chapter 2 General IED application The report record includes tripping, alarm and operation reports. See Chapter 23 General report list for detail. 11

26 Chapter 2 General IED application 3 Disturbance recorder 3.1 Introduction To get fast, complete and reliable information about fault current, voltage, binary signal and other disturbances in the power system is very important. This is accomplished by the disturbance recorder function and facilitates a better understanding of the behavior of the power system and related primary and secondary equipment during and after a disturbance. An analysis of the recorded data provides valuable information that can be used to explain a disturbance, basis for change of IED setting plan, improvement of existing equipment etc. The disturbance recorder, always included in the IED, acquires sampled data from measured analogue quantities, calculated analogue quantity, binary input and output signals. The function is characterized by great flexibility and is not dependent on the operation of protection functions. It can even record disturbances not tripped by protection functions. The disturbance recorder information is saved for each of the recorded disturbances in the IED and the user may use the local human machine interface or dedicated tool to get some general information about the recordings. The disturbance recording information is included in the disturbance recorder files. The information is also available on a station bus according to IEC and IEC Fault wave recorder with great capacity, can record full process of any fault, and can save the corresponding records. Optional data format or wave format is provided, and can be exported through serial port or Ethernet port by COMTRADE format. 3.2 Setting Abbr. Explanation Default Unit Min. Max. T_Pre Fault Time setting for recording time before fault occurred 0.05 s T_Post Fault Time setting for recording time after fault occurred 1 s DR_Sample Rate Sample rate for fault recording

27 Chapter 2 General IED application Abbr. Explanation Default Unit Min. Max. (0: 600 sample/cycle, 1:1200 sample/cycle) 13

28 Chapter 2 General IED application 4 Self supervision function 4.1 Introduction The IED may test all hardware components itself, including loop out of the relay coil. Watch can find whether or not the IED is in fault through warning LED and warning characters which show in liquid crystal display and display reports to tell fault type. The method of fault elimination is replacing fault board or eliminating external fault. 4.2 Self supervision principle Measuring the resistance between analog circuits and ground Measuring the output voltage in every class Checking the zero drift and scale Verifying alarm circuit Verifying binary input Checking actual live tripping including circuit breaker Checking the setting values and parameters 4.3 Self supervision report Table 1 Self supervision report Abbr.(LCD Display) Sample Err Soft Version Err EquipPara Err ROM Verify Err Setting Err Set Group Err BO No Response Description AI sampling data error Soft Version error Equipment parameter error CRC verification for ROM error Setting value error Pointer of setting group error Binary output (BO) no response 14

29 Chapter 2 General IED application Abbr.(LCD Display) BO Breakdown SRAM Check Err FLASH Check Err BI Config Err BO Config Err BI Comm Fail BO Comm Fail Test BO Un_reset BI Breakdown DI Input Err NO/NC Discord BI Check Err BI EEPROM Err BO EEPROM Err Sys Config Err Battery Off Meas Freq Alarm Not Used Trip Fail PhA CB Open Err PhB CB Open Err PhC CB Open Err 3Ph Seq Err AI Channel Err 3I0 Reverse 3I0 Imbalance Description Binary output (BO) breakdown SRAM check error FLASH check error BI configuration error BO configuration error BI communication error BO communication error Test BO unreset BI breakdown BI input error NO/NC discordance BI check error BI EEPROM error BO EEPROM error System Configuration Error Battery Off Measurement Frequency Alarm Not used Trip fail PhaseA CB position BI error PhaseB CB position BI error PhaseC CB position BI error Three phase sequence error AI channel error 3I0 reverse 3I0 imbalance 15

30 Chapter 2 General IED application 5 Time synchronization 5.1 Introduction Use the time synchronization source selector to select a common source of absolute time for the IED when it is a part of a protection system. This makes comparison of events and disturbance data between all IEDs in a SA system possible. 5.2 Synchronization principle Time definitions The error of a clock is the difference between the actual time of the clock, and the time the clock is intended to have. The rate accuracy of a clock is normally called the clock accuracy and means how much the error increases, i.e. how much the clock gains or loses time. A disciplined clock is a clock that knows its own faults and tries to compensate for them, i.e. a trained clock. Synchronization principle From a general point of view synchronization can be seen as a hierarchical structure. A module is synchronized from a higher level and provides synchronization to lower levels. A module is said to be synchronized when it periodically receives synchronization messages from a higher level. As the level decreases, the accuracy of the synchronization decreases as well. A module can have 16

31 Chapter 2 General IED application several potential sources of synchronization, with different maximum errors, which gives the module the possibility to choose the source with the best quality, and to adjust its internal clock from this source. The maximum error of a clock can be defined as a function of: The maximum error of the last used synchronization message The time since the last used synchronization message The rate accuracy of the internal clock in the module Synchronization from IRIG The built in GPS clock module receives and decodes time information from the global positioning system. The module is located on the Communication Module (MASTER). The GPS interfaces to the IED supply two possible synchronization methods, IRIGB and PPS (or PPM) Synchronization via PPS or PPM The IED accepts PPS or PPM to the GPS interfaces on the Communication Module. These pulses can be generated from e.g. station master clock. If the station master clock is not synchronized from a world wide source, time will be a relative time valid for the substation. Both positive and negative edges on the signal can be accepted. This signal is also considered as a fine signal Synchronization via SNTP SNTP provides a Ping-Pong method of synchronization. A message is sent from an IED to an SNTP-server, and the SNTP-server returns the message after filling in a reception time and a transmission time. SNTP operates via the normal Ethernet network that connects IEDs together in an IEC61850 network. For SNTP to operate properly, there must be a SNTP-server present, preferably in the same station. The SNTP synchronization provides an accuracy that will give 1ms accuracy for binary inputs. The IED itself can be set as a SNTP-time server. 17

32 Chapter 2 General IED application 6 Setting 6.1 Introduction Settings are divided into separate lists according to different functions. The printed setting sheet consists of two parts -setting list and communication parameters. 6.2 Operation principle The setting procedure can be ended at the time by the key SET or QUIT. If the key SET is pressed, the display shows the question choose setting zone. The range of setting zone is from 1 to 16. After confirming with the setting zone-key SET, those new settings will be valid. If key QUIT is pressed instead, all modification which have been changed will be ignored. 18

33 7 Authorization 7.1 Introduction Chapter 2 General IED application To safeguard the interests of our customers, both the IED and the tools that are accessing the IED are protected, subject of authorization handling. The concept of authorization, as it is implemented in the IED and the associated tools is based on the following facts: There are two types of points of access to the IED: local, through the local HMI remote, through the communication ports There are different levels (or types) of guest, super user and protection engineer that can access or operate different areas of the IED and tools functionality. 19

34 Chapter 2 General IED application 20

35 Chapter 3 Overcurrent protection Chapter 3 Overcurrent protection About this chapter This chapter describes the protection principle, input and output signals, parameter, IED report and technical data used for overcurrent protection. 21

36 Chapter 3 Overcurrent protection 1 Overcurrent protection 1.1 Introduction The directional/non-directional overcurrent protection function can be applied as backup protection functions in various applications for transmission lines. The directional overcurrent protection can be used based on both the magnitude of the fault current and the direction of power flow to the fault location such as parallel lines. Main features of the overcurrent protection are as follows: Two definite time stages One inverse time stage 11 kinds of IEC and ANSI inverse time characteristic curves as well as optional user defined characteristic Selectable directional element characteristic angle to satisfy the different network conditions and applications Each stage can be set individually as directional/non-directional, Directional element can be set to be forward toward the protected object or reverse toward system for all stages Each stage can be set individually for inrush restraint Cross blocking function for inrush detection Settable maximum inrush current VT secondary circuit supervision for directional protection. Once VT failure happens, the directional stage can be set to be blocked or to be non-directional stage 1.2 Protection principle Time characteristic The IED is designed with three overcurrent protection stages of which two 22

37 Chapter 3 Overcurrent protection stages operate as definite overcurrent stages and the other one operates with inverse time-current characteristic. 11 kinds of inverse time characteristics are available. It is also possible to create a user defined time characteristic. Each stage can operate in conjunction with the integrated inrush restraint, directional functions and operate based on measured phase current. Furthermore, each stage is independent from each other and can be combined as desired. Pickup value for the definite stage can be set in setting value. Each phase current is compared with the corresponding setting value with delay time. If currents exceed the associated pickup value, after expiry of the time delay, the trip command is issued. The pickup value for inverse time stage can be set in setting value. The measured phase currents are compared with corresponding setting value and if any phase exceeds that setting, the protection will issue a trip command with corresponding delay time. The time delay of inverse time characteristic is calculated based on the type of the set characteristic, the magnitude of the current and a time multiplier. For the inverse time characteristic, both ANSI and IEC based standard curves are available, and any user-defined characteristic can be defined using the following equation: t = i I_OC A_OC p _OC 1 + B_OC K_OC Equation 1 where: A_OC: Time factor for inverse time stage B_OC: Delay time for inverse time stage P_OC: index for inverse time stage K_OC: Time multiplier Inrush restraint feature The IED may detect large magnetizing inrush currents during transformer energizing. Inrush current comprises large second harmonic current which 23

38 Chapter 3 Overcurrent protection does not appear in short circuit current. Therefore, inrush current may affect the protection functions which will operate based on the fundamental component of the measured current. Accordingly, inrush restraint logic is provided to prevent overcurrent protection from maloperation. The inrush restraint feature operates based on evaluation of the 2 nd harmonic content which is present in measured current. The inrush condition is recognized when the ratio of second harmonic current to fundamental component exceeds the corresponding setting value for each phase. The setting value is applicable for both definite time stage and inverse time stage. The inrush restraint feature will be performed as soon as the ration exceeds the set threshold. Furthermore, by recognition of the inrush current in one phase, it is possible to set the protection in a way that not only the phase with the considerable inrush current, but also the other phases are blocked for a certain time. This is achieved by cross-blocking feature integrated in the IED. The inrush restraint function has a maximum inrush current setting. Once the measuring current exceeds the setting, the overcurrent protection will not be blocked any longer Direciton determination feature The direction detection is performed by determining the position of current vector in directional characteristic. In other word, it is done by comparing phase angle between the fault current and the reference voltage. Figure 1 illustrates the direction detection characteristic for phase A element. Two operation areas are provided for direction determination, the forward area toward the protected object and the reverse area toward the system, which are shown in Figure 1. Forward 90 I A ΦPh_Char 0 U BC_Ref I A Reverse 24

39 Chapter 3 Overcurrent protection Figure 1 Direction detection characteristic of overcurrent protection directional element where: Ф Ph _Char: The settable characteristic angle The assignment of the applied measuring values used in direction determination shows in Table 2 for different types of faults. Table 2 Assignment of current and reference voltage for directional element Phase Current Voltage A B C I a Ib I c U bc U ca U ab For three-phase short-circuit fault, without any healthy phase, memory voltage values are used to determine direction clearly if the measured voltage values are not sufficient. The detected direction is based on the memory voltage of previous power cycles. If VT fail happen (a short circuit or broken wire in the voltage transformer's secondary circuit or voltage transformer fuse), the protection can be set to be blocked or to be applied as non-directional overcurrent protection Logic diagram The following logic diagram is applicable for phase A. Phase B and phase C logic diagrams are similar with the phase A logic. 25

40 Chapter 3 Overcurrent protection Ia>I_OC1 OC Dir To Sys VT fail AND 1 OC1 Direction Off OC1 Direction On AND OC Dir To Equip VT fail AND OR 0 OC1 Inrush Block Off <Imax_2H_UnBlk Ia2/Ia1> AND OC1 Inrush Block On T_OC1 0 OC_Inrush Block Off AND Func_OC1 Trip Cross blocking OC_Inrush Block On Ia2/Ia1 > Ib2/Ib1 > OR Ic2/Ic1 > AND Cross blocking T2h_Cross_Blk< Figure 2 Logic diagram for phase A of overcurrent protection 1.3 Input and output signals 26

41 Chapter 3 Overcurrent protection IP1 IP2 IP3 UP1 UP2 UP3 Relay Startup OC1_Trip OC2_Trip OC Inv Trip Table 3 Analog input list Signal Description IP1 Signal for current input 1 IP2 Signal for current input 2 IP3 Signal for current input 3 UP1 Signal for voltage input 1 UP2 Signal for voltage input 2 UP3 Signal for voltage input 3 Table 4 Binary output list Signal Relay Startup Trip 3Ph OC1_Trip OC2_Trip OC Inv Trip Description Relay startup Trip three phases Overcurrent protection stage 1 trip Overcurrent protection stage 2 trip Overcurrent protection inverse time stage trip 1.4 Setting parameters Setting list Table 5 Overcurrent protection function setting list Parameter Description Default Unit Min. Max. I_OC1 Current setting for stage 1 2In A T_OC1 Time setting for stage s I_OC2 Current setting for stage 2 1.2In A T_OC2 Time setting for stage s Curve_OC Inv Inverse time curve I_OC Inv Current setting for inverse time 1.2In A

42 Chapter 3 Overcurrent protection Parameter Description Default Unit Min. Max. stage K_OC Inv Time multiplier for inverse time stage A_OC Inv Time factor for inverse time stage 0.14 s B_OC Inv Delay time for inverse time stage 0 s P_OC Inv Index for inverse time stage Angle_OC Direction characteristic angle 60 Degree Imax_2H_UnBlk Maximum inrush current setting 5In A Ratio_I2/I1 Ratio for second harmonic current to fundamental component T2h_Cross_Blk Time for cross blocking 1 s Table 6 Overcurrent protection binary setting list Name Description Default Unit Min. Max. Func_OC1 OC1 Direction OC1 Dir To Sys OC1 Inrush Block Func_OC2 OC2 Direction OC2 Dir To Sys OC2 Inrush Block Func_OC Inv OC Inv Direction OC Inv Dir To Sys OC Inv Inrush Block Overcurrent stage 1 enabled or disabled Direction of overcurrent stage 1 enabled or disabled Direction toward system (0) or toward equipment (1) for stage Inrush restraint for overcurrent stage 1 enabled or disabled Overcurrent stage 2 enabled or disabled Direction of overcurrent stage 2 enabled or disabled Direction toward system (0) or toward equipment (1) for stage Inrush restraint for overcurrent stage 2 enabled or disabled Inverse time stage for overcurrent enabled or disabled Direction of inverse time stage enabled or disabled Direction toward system (0) or toward equipment (1) for inverse time stage Inrush restraint for inverse time stage enabled or disabled Blk OC at VT VT failure block overcurrent protection

43 Chapter 3 Overcurrent protection Name Description Default Unit Min. Max. Fail enabled or disabled OC Init CBF Overcurrent protection initiate CBF protection enabled or disabled Reports Table 7 Event report list Information OC1 Trip OC2 Trip OC Inv Trip Description Overcurrent stage 1 trip Overcurrent stage 2 trip Inverse time stage of overcurrent protection trip 1.6 Technical data NOTE: Ir: CT rated secondary current, 1A or 5A; In: nominal current of the reference side of transformer; Table 8 Overcurrent protection technical data Item Rang or Value Tolerance Definite time characteristics Current 0.08 Ir to Ir ±3% setting or ±0.02Ir Time delay 0.00 to 60.00s, step 0.01s Reset time approx. 40ms Reset ratio Approx at I/In 0.5 Inverse time characteristics ±1% setting or +40ms, at 200% operating setting Current 0.08 Ir to Ir ±3% setting or ±0.02Ir IEC standard ANSI Normal inverse; Very inverse; Extremely inverse; Long inverse Inverse; Short inverse; Long inverse; Moderately inverse; Very inverse; Extremely inverse; ±5% setting + 40ms, at 2 <I/I SETTING < 20, in accordance with IEC ±5% setting + 40ms, at 2 <I/ISETTING < 20, in accordance with ANSI/IEEE C37.112, 29

44 Chapter 3 Overcurrent protection Definite inverse user-defined characteristic T= A + B k ±5% setting + 40ms, at 2 i ( I_SET )P 1 <I/I SETTING < 20, in accordance with IEC Time factor of inverse time, to 200.0s, step 0.001s A Delay of inverse time, B to 60.00s, step 0.01s Index of inverse time, P to 10.00, step set time Multiplier for step n: 0.05 to 999.0, step 0.01 k Minimum operating time Maximum operating time Reset mode Reset time 20ms 100s instantaneous approx. 40ms, Directional element Operating area range 170 ±3, at phase to phase Characteristic angle 0 to 90, step 1 voltage >1V Table 9 Inrush restraint function Item Range or value Tolerance Upper function limit Max current for inrush 0.25 Ir to Ir ±3% setting value or ±0.02Ir restraint Ratio of 2 nd harmonic current 0.10 to 0.45, step 0.01 to fundamental component current Cross-block (IL1, IL2, IL3) 0.00s to s, step 0.01s ±1% setting or +40ms (settable time) 30

45 Chapter 4 Earth fault protection Chapter 4 Earth fault protection About this chapter This chapter describes the protection principle, input and output signals, parameter, IED report and technical data used for earth fault protection. 31

46 Chapter 4 Earth fault protection 1 Earth fault protection 1.1 Introduction The earth fault protection can be used to clear phase to earth faults as system back-up protection. The earth fault protection is can also be applied for coordination based on both magnitude of earth fault current and the direction of power flow to the fault location. The protection provides the following features: Two definite time stages One inverse time stage 11 kinds of the IEC and ANSI inverse time characteristic curves as well as optional user defined characteristic Zero sequence directional element Negative sequence directional element can be applied as a supplement to zero sequence directional element. It can be enabled/disabled by setting Each stage can be set individually as directional/non-directional Directional element can be set to be forward toward the protected object or reverse toward system for all stages Settable directional element characteristic angle to satisfy the different network conditions and applications Each stage can be set individually for inrush restraint Settable maximum inrush current VT secondary circuit supervision for directional protection function. Once VT failure happens, the directional stage can be set to be blocked or to be non-directional Zero-sequence current is calculated using summation of 3 phase currents or measured from 4 th phase CT (selectable) 32

47 Chapter 4 Earth fault protection Zero-sequence voltage calculated by summation of 3 phase voltage or measured from earth phase VT selectable 1.2 Protection principle Time characteristic The IED is designed with three earth fault protection stages of which two stages operate as definite earth fault stages and the other one operates with inverse time-current characteristic. All stages can operate in conjunction with the integrated inrush restraint and directional functions. This protection function can operate based on the zero-sequence current which is calculated by summation of three phase currents or measured from earth phase CT Furthermore, the stages are independent from each other and can be combined as desired. They can be enabled or disabled by dedicated binary setting. Individual pickup value for each definite stage can be defined in setting value. By applying the settings, the measured zero sequence current is compared separately with the setting value for each stage. If zero-sequence current exceed the associated pickup value, after expiry of the time delay, the trip command is issued. The time delay of inverse time characteristic is calculated based on the type of the set characteristic, the magnitude of the current and a time multiplier. For the inverse time characteristic, both ANSI and IEC based standard curves are available, and any user-defined characteristic can be defined using the following equation: t = i I_EF A_EF p _EF 1 + B_EF K_EF Equation 2 where: A_EF: Time factor for inverse time stage B_EF: Delay time for inverse time stage P_EF: index for inverse time stage 33

48 Chapter 4 Earth fault protection K_EF: Time multiplier The time is set to count up for a user-defined time delay. The time delay can be set for each definite stage individually through corresponding settings. After the user-defined time delays elapsed, a trip command is issued Inrush restraint feature The IED may detect large magnetizing inrush currents during transformer energizing. Inrush current comprises large second harmonic current which does not appear in short circuit current. Therefore, inrush current may affect the protection functions which will operate based on the fundamental component of the measured current. Accordingly, inrush restraint logic is provided to prevent earth fault protection from maloperation. The inrush restraint feature operates based on evaluation of the 2 nd harmonic content which is present in measured current. The inrush condition is recognized when the ratio of second harmonic current to fundamental component exceeds the corresponding setting value for each phase. The condition for phase current inrush or zero sequence current inrush can be selected by binary setting. The setting value is applicable for both definite time stage and inverse time stage. The inrush restraint feature will be performed as soon as the ratio exceeds the set threshold. The inrush restraint function has a maximum inrush current setting. Once the measuring current exceeds the setting, the earth fault protection will not be blocked any longer Direction determination feature The integrated directional function can be applied to each stage of earth fault element via binary setting. There are two direction elements for direction determination of earth faults. The first is based on zero sequence components and the second is based on negative sequence components. During direction determination by directional function (using zero or negative sequence components), a VT fail condition may result in false or undesired tripping by directional earth fault element. Therefore, under the VT failure situation, it can be set to block directional earth fault protection or to apply non-directional earth fault protection. The following subsections go on to demonstrate basic principle of these two direction element. 34

49 Chapter 4 Earth fault protection Zero sequence directional element In this method, the direction determination is performed by comparing the zero sequence quantities. In current path, the zero sequence current is calculated from the sum of the three phase currents or measured from earth CT. In the voltage path, the zero sequence voltage (3U 0 ) is used as reference voltage if it is connected. Otherwise, the zero sequence voltage, is calculated from the sum of the three phase voltages. In order to satisfy different network conditions and applications, the reference voltage can be rotated by adjustable angle between 0 and 90 in clockwise direction (negative sign). It should be noted that the settings affect all the directional stages of earth fault element. In this way, the vector of rotated reference voltage can be closely adjusted to the vector of fault current -3I0 which lags the fault voltage 3V 0 by the fault angle Φ 0 _Char. This would provide the best possible result for the direction determination. The rotated reference voltage defines the forward and reverse area. Figure 3 shows an example of direction determination. Bisector -3I0 90 Reverse 0 3U0_Ref Φ0_Char Forward -3I 0 Bisector Figure 3 Direction detection characteristic of earth fault protection directional element Negative sequence directional element This method is particularly suitable in case of too low zero sequence voltage due to some fault condition e.g. when a considerable zero sequence mutual coupling exists between parallel lines or there is an unfavorable zero sequence impedance. In such cases it may be desirable to determine direction of fault current by using negative sequence components. To do so, it is required to enable the negative sequence directional element in setting 35

50 Chapter 4 Earth fault protection value. By applying this setting, the default direction determination of earth fault current is performed by the zero sequence element. However, when the magnitude of zero sequence voltage falls below permissible threshold of 1V and negative sequence voltage is larger than 2V, the negative sequence element is in service for direction determination. On the contrary, if the negative sequence directional element is disabled, the direction of earth fault current is only determined by using the zero sequence element. In this regard, if the zero sequence voltage has a magnitude larger than 1V, proper determination of fault direction is performed. However, for the condition that zero sequence voltages below 1V, no direction determination would be possible. Thus, the fault is assumed to be in reverse direction. Accordingly, for the negative sequence element, the direction determination is performed by comparing the negative sequence system quantities. To do so, three times of the calculated negative sequence current 3I 2 (3I 2 =I A +a 2 I B +ai C ) is compared with three times of the calculated negative sequence voltage 3V 2 (3V 2 =V A +a 2 V B +av C ) as reference voltage, where a is equal to e j120. The fault current -3I 2 is opposite to the fault current 3I 2 and lags from the voltage 3V 2 by the fault angle, which is a setting value defined in setting value. In order to satisfy different applications, the reference voltage can be rotated by adjustable angle between 0 and 90 in clockwise direction (negative sign) to be closely adjusted to the vector of fault current -3I 2. This would provide the best possible result for the direction determination. The rotated reference voltage defines the forward and reverse area. Figure 4 shows an example of direction determination. Bisector -3I 2 90 Reverse 0 3U 2_ Ref Φ2_Char Forward -3I 2 Bisector Figure 4 Direction detection characteristic of negative sequence directional element Logic diagram 36