MPR 10. Digital Motor Protection Relay. P&B Engineering Belle Vue Works Boundary Street Manchester M12 5NG

Transcription

1 MPR 10 Digital Motor Protection Relay P&B Engineering Belle Vue Works Boundary Street Manchester M12 5NG Tel: Fax:

2 Issue 3 8/10/98 Contents 1. INTRODUCTI APPLICATI FEATURES AND CHARACTERISTICS DESIGN CIRCUIT DIAGRAM Analogue Input Circuits Output Relays FRT PANEL Fault Indication REMOTE DATA COMMUNICATI FRT PANEL CIRCUIT DIAGRAM MOUNTING INFORMATI SERIAL NUMBER WORKING PRINCIPLES ANALOGUE CIRCUITS DIGITAL CIRCUITS POWER SUPPLY REQUIREMENTS FOR THE MAIN CURRENT TRANSFORMERS... 9 CT CLASS 3, 2.5VA OPERATI AND SETTING LAYOUT OF THE CTROL ELEMENTS SETTING PROCEDURE Overload Pre-Trip Alarm Earth Fault Current (Ie) Locked Rotor ( Stall ) Protection Undercurrent Setting (Iu) Negative Phase Sequence Protection Reset Full Load Current Setting (Iflc) t6x Setting Normal/Factory Mode OVERCURRENT TRIP INHIBIT SETTING VALUE CALCULATI RELAY CASE TEST AND MAINTENANCE TECHNICAL DATA MEASURING INPUT CIRCUITS AUXILIARY POWER SUPPLY SETTING RANGES AND STEPS THERMAL CURRENT / TIME CURVES OUTPUT CTACT RATINGS SYSTEM DATA HOUSING PUBLICATI CHANGES ORDER FORM

3 1. Introduction. The application of powerful microprocessors opens a new chapter for power system protective relaying. The digital processing of measured values and the ability to perform complex arithmetic and logic operations, give digital protection relays significant performance and flexibility improvements over their traditional analogue counterparts. Additional advantages - very small power consumption, adaptability, self-supervision, fault diagnosis through fault data recording, smaller physical construction and selectable relay characteristics - all combine to allow the implementation of accurate and highly reliable protection schemes at a significantly reduced financial burden. The development of microprocessor based protective relays and their introduction into the market has been stimulated by the recent trend to replace analogue with digital equipment. This modern trend has prompted the development of a new P&B protective relay family - the MR relay series. This comprehensive family of protection relays can satisfy the demands of even the most complex protection schemes: MRI - Overcurrent Relay (Independent time/i.d.m.t + earth + directional facilities) MRI-V - Voltage Dependent Overcurrent Relay MREF - Restricted Earth Fault Relay MRMF - Mains Failure Relay MRNS - Negative Sequence Relay MRRP - Power Relay MRCS - Check Synchronising Relay MRFF - Field Failure Relay The superiority of digital protective relaying over traditional analogue devices, as embodied by the MR relay family, is summarised by the following features: Integration of many protective functions in a single compact case High accuracy owing to digital processing Digital relay setting with very wide setting ranges and fine setting steps Comfortable setting procedure through extensive human - relay dialogue Measured values and fault data indication by means of alpha-numeric display Data exchange with DCS/SCADA by means of RS485 Operational reliability through self-supervision A similar but simplified range, with reduced functions and without display, is also available. The MIRI - overcurrent and earth fault relays, and the MIRV - undervoltage, overvoltage and neutral voltage displacement relays. To complement the MR series, a range of Auxiliary, Timing and Tripping devices are also available. The MPR range of motor protection relays embodies the developments in technology of the MRI, and MIRI as well as previous electronic motor protection relays, with the traditional knowledge and expertise developed over the long tradition of motor protection within P & B Engineering. Issue 3 8/10/98 Page 1 MPR10

4 2. Application. The MPR 10 is a universal digital adjustable motor protection relay. It serves as overload, negative phase sequence (unbalance), and general protection for synchronous and induction machines. With a large selection of adjustment possibilities, the MPR 10 is suitable for almost any type of machine. The protective functions of the MPR 10 are summarised as follows: Thermal overload protection with adjustable current/time curves. Thermal Overload prior alarm with separate output relay Locked rotor and stall protection. (definite time). Earth fault protection (definite time). Negative phase sequence protection (inverse time). Undercurrent protection (definite time). Setting and measured parameters available via RS485 serial link. 3. Features And Characteristics. High accuracy. Wide setting range. Universal power supply AC or DC. Selectable auto / manual reset of the output relays. Hot/cold thermal current/times with thermal memory and trip times dependent on prior loading. Locked rotor protection set at 3.5 times I FLC after the start time. Setting via front panel switches and potentiometers. Test functions activated with front panel push button. Complete digital processing of the sampled measured values Continuous self-supervision of software and hardware Setting Values and Measured Data are available via optional RS485 serial link. Din rail modules for back of panel mounting, allowing a considerable saving in front panel space. Issue 3 8/10/98 Page 2 MPR10

5 4. Design Circuit Diagram. L1 L2 L3 Supply A2 A1 P2 S2 1S1 P1 S1 1S2 2S1 2S2 3S1 3S2 I1 I2 IE POWER SUPPLY TRIP ALARM MPR Typical earthing shown. Diagram 1 Relay with two line current transformers and a core balance current transformer. L1 L2 L3 Supply A2 A1 P2 S2 1S1 P1 S1 1S2 2S1 2S2 3S1 3S2 I1 I2 IE POWER SUPPLY TRIP ALARM MPR Diagram 2 Relay with three line current transformers residually connected to provide earth fault and NPS protection. Issue 3 8/10/98 Page 3 MPR10

6 Analogue Input Circuits. The constantly monitored measuring values are galvanically decoupled, filtered and finally fed to the analogue/digital converter. The protection unit receives these analogue input signals of the phase currents I1 & I2 and Earth fault IE, via separate input transformers Output Relays. The MPR 10 has two output relays, with single pole change-over contacts as detailed in the previous diagram and summarised below: Tripping relay Alarm relay The trip relay is energised for ' trip' and de-energised for 'no trip'. The alarm relay is energised for 'no alarm' and de-energised for 'alarm'. Its action is the inverse of the trip relay to allow flexibility in plant wiring schemes. The trip relay will operate for 1 second if the test button is pressed Front Panel. The front panel of the MPR 10 comprises the following operation and indication elements: 8 Dip switches for selection of protection options. 6 Rotary switches for setting of parameters. 3 LEDs for indication. 1 Push button for reset and test functions. Issue 3 8/10/98 Page 4 MPR10

7 Fault Indication. When the relay alarms or trips the LEDS on the front panel will flash indicating the type of fault the relay is seeing, as shown in Diagram 3 below. The LED flashes a certain number of times very quickly, pauses then repeats the process. The LED will carry on indicating the fault until it has been cleared. For example the Trip LED flashing four times indicates that there is an unbalance fault on the relay. This then enables the user to clear the fault that is causing the trip. FUNCTI TRIP LED OVERLOAD LED LED THERMAL PICKUP OVERLOAD PRE-ALARM OVERLOAD TRIP WHEN MANUAL RESET POSSIBLE STALL PROTECTI EARTH FAULT UNDERLOAD UNBALANCE SHORT CIRCUIT INTERNAL FAULT Diagram 3 Tripping And Alarm Indications. Issue 3 8/10/98 Page 5 MPR10

8 5. Remote Data Communication. As an option, the MPR 10 may have a separate RS485 interface for remote data communication with a control centre. This then enables the user to view many of the parameters of the relay as well as well as assigning new values to the parameter. Auxilliary supply to the unit is in the range 19-55v DC only. For more information on the communications of an MPR10 contact P&B Engineering on Tel: The unit, which must be mounted adjacent to the protection relay, provides the following information: Status signals Self supervision alarm signal Actual measured values Relay settings Fault signalling 5.1. Front Panel. The front panel of the communications unit shows the following data: 2 LEDs displaying power status and communication activity A1 PE A2 A1 PE A2 RS XRS1 RS RS N G P N G P 1 Jumper to switch or the communication facilities of the unit Circuit Diagram. -ve Gnd +ve Input Supply 19-55v DC L- L+ P G N PE PE A1 A2 POWER SUPPLY A2 A1 L+ Output Supply 19-55v DC L- N G -ve Gnd +ve P MPR 10 COMMUNICATI UNIT Issue 3 8/10/98 Page 6 MPR10

9 5.3. Mounting Information. The Communications Unit is mounted next to the MPR10 as shown below. Also shown are the dimensions of the Unit A1 PE A2 A1 PE A2 RS XRS1 RS RS N G P N G P Positioning Of Communications Unit. 110 Din rail mounting: Top Hat Profile to BS5584:1978 (EN , DIN ) A1 PE A2 A1 PE A2 RS XRS1 RS RS N G P N G P 1S1 1S2 2S1 2S2 3S1 3S2 A1 TEST I> I>> I> In I>> In ti> ti>> A All dimensions are approximate and in mm 5.4. Serial Number. To set the serial number follow the procedure below. i) Set dip switch 8 to on and dip switch 7 to off. ii) Set dips 1 through 5 to the required comms ID. (0 = off, 1-31 = comms id). iii) Power up the unit. iv) Press the test/reset button. v) The alarm and overload LEDs will flash momentarily. vi) Power off the unit and reset the dip switches to their previous settings. Issue 3 8/10/98 Page 7 MPR10

10 6. Working Principles Analogue Circuits. The incoming currents and voltages from the external transformers are converted to internal signals in proportion to the current, via the internal input transducers and shunt resistors. The noise signals caused by inductive and capacitive coupling are suppressed by an analogue filter circuit. The analogue signals are fed to the A/D converter of the micro-processor and transformed to digital signals through sample-hold circuits. The analogue signals are sampled at a rate of 470Hz giving a sample time of 2.13mS for each measured value Digital Circuits. The essential component of the MPR 10 relay is a powerful micro-processor. All of the operations, from the analogue digital conversion to the relay trip decision, are carried out by the microprocessor. The relay has a thermal memory which operates using an I 2 t characteristic and a fixed hot / cold ratio of 50%. A motor running at FLC (Full Load Current - Iflc) in the steady state achieves a thermal capacity of 45%. At operating currents above 105% the relay will trip in a time proportional to current. That is a trip occurs at a thermal capacity of 100%. The thermal characteristics are adjustable through the potentiometer setting t6x. which is the time, in seconds, for the relay to trip at six times FLC (Iflc). The thermal current/time functions of the relay have the following special features:- 1. The change in thermal capacity during a start is stored and a reset after a trip is only allowed if there is this much capacity available. For example if during a start the thermal capacity rises from 75% to 95% a required start capacity of 20% is stored. After an overload trip the relay will not reset until the thermal capacity has dropped to less than (100%-20%) = 80%. To allow faster restarts there is a maximum value of 50% for the stored change in thermal capacity. 2. After a motor has tripped on thermal overload the thermal capacity available in the relay for a restart is increased at a rate according to the cooling time constant of the relay. The motor cannot be restarted until there is sufficient capacity, as above, available. 3. If the motor is started from cold and then stopped, an immediate restart would only be possible if there was sufficient thermal capacity available within the relay. The thermal capacity is retained even when the auxiliary supply is disconnected. Under special circumstances it is possible to 'defeat' this mechanism, that is reset the thermal capacity to zero, by holding the test button down as the auxiliary supply is applied. 4. There is a pre-trip alarm relay output available and may be switched on or off using the relay front panel setting switch (dip switch 1). The alarm output is set at 95% thermal capacity. The alarm is self reset, that is when the thermal capacity rises above 95% the alarm is switched on and when the thermal capacity drops below 95% the alarm is switched off. 5. On power up the thermal model is initialised to the value it had just prior to removal of the auxiliary supply. 6. The overload LED fitted to the front panel of the unit will be illuminated when the motor current is greater than 105% of FLC. This LED will also be illuminated when a thermal overload trip has occurred. Issue 3 8/10/98 Page 8 MPR10

11 6.3. Power Supply. The MPR10 needs a seperate auxiliary supply voltage. The relay has an integrated wide range power supply with voltage in the range:- Vaux = v AC Vaux = v DC The voltage does not need to be set Requirements For The Main Current Transformers. In order to ensure the correct operation of the MPR 10 range of relays, protection class CT's must be utilised. Instrument CT's are generally NOT a suitable alternative. CT's should be chosen such that saturation, or loss of accuracy does not occur within the settings and operation ranges of the relays. In the absence of known settings the following may be regarded as an approximate guide. For 1A secondary CT class 5P10 or 10P10 2.5VA (Allowing for up to 1.5Ω of secondary lead resistance) For 5A secondary CT class 5P10 or 10P10 2.5VA (Allowing for up to 0.8Ω of secondary lead resistance) with due regard to a suitable CT ratio and fault level capacity. For Core Balance CT (CBCT) CT class 3, 2.5VA 7. Operation And Setting Layout Of The Control Elements. All control elements required for the operation and adjustment of the MPR 10 are located on the front panel. They are divided according to function into the two following groups: DIP SWITCHES: Selection of the protection functions to be utilised. These are detailed in the table below: Normal operation dip switch functions. DIP Switch Function 1 Overload pre trip alarm ( / ). 2 Earth fault and locked rotor protection ( / ). 3 Undercurrent protection ( / ). 4 NPS protection ( / ). 5 Contactor ()/ Circuit breaker () feeder selection. 6 Overload reset auto () / man (). 7 Earth fault, nps and locked rotor reset auto () / man (). 8 Normal Operation () Issue 3 8/10/98 Page 9 MPR10

12 ROTARY SWITCHES: Individual setting of trip levels or time characteristics. These are detailed in the table below: Control settings. Potentiometer Function. 1. Iflc/Inom ratio coarse six steps 0.6, 0.7, 0.8, 0.9, 1.0, Iflc/Inom ratio fine variable from 0 to t 6x time coarse six steps 0, 5, 10, 15, 20, 25 seconds. (see note) 4. t6x time fine variable from 0 to 5 seconds. 5. Iuc/Iflc ratio variable from 40% to 80%. 6. I ef/ I flc ratio variable from 10% to 50%. NOTE When the t6x setting is set at its lowest setting ( 0.0 ) the actual setting assumed by the relay is 0.5 Seconds 7.2. Setting Procedure. In the following sections the setting of all relay parameters is described in detail: Overload Pre-Trip Alarm. The pre-trip alarm relay output may be switched on or off using the relay front panel setting switch ( DIP Switch 1). The alarm output is set at 95% thermal capacity. The alarm is self reset, that is when the thermal capacity rises above 95% the alarm is switched on and when the thermal capacity drops below 95% the alarm is switched off Earth Fault Current (Ie). This setting specifies the pickup level of Earth Fault Current as a percentage of Iset. The value is set by adjusting the potentiometer on the front panel. The earth fault protection function may be switched on or off using the relay front panel setting switch (dip switch 2). The action on earth fault is to trip. The earth fault trip level setting is variable between 10% and 50% of Inom. The earth fault current is detected by the connection of the earth fault input either to a core balance current transformer or to three line current transformers residually connected. If the earth fault current rises above the set level for a time greater than the set earth fault operating time the relay will trip. The earth fault protection is automatically or manually reset as determined by dip switch 7. The earth fault trip operates in a definite time of 1 second or instantaneously as determined by dip switch 5. The earth fault trip is instantaneous when dip switch 5 is on (Circuit breaker mode) and 1 second when dip switch 5 is set to off (contactor fed mode) Locked Rotor ( Stall ) Protection. Stalling protection is available and may be switched on or off using the relay front panel setting switch ( DIP Switch 2). Stalling protection is activated by detection of the end of the start time. Stall protection is set to trip at 3.5 times I flc. The locked rotor trip operates in a definite time of 1 second. The locked rotor protection is automatically or manually reset as determined by dip switch 7. Issue 3 8/10/98 Page 10 MPR10

13 Undercurrent Setting (Iu). The undercurrent protection function may be switched on or off using the relay front panel setting switch (dip switch 3). The action on undercurrent is to alarm. The undercurrent setting is variable between 40% and 80% of the motor FLC (Iflc) via the potentiometer on the relay front panel.. If after a start the average motor current drops below the set undercurrent level for a time greater than the set undercurrent time (3 sec.) the relay will alarm. The undercurrent protection is automatically reset Negative Phase Sequence Protection. The negative phase sequence protection function may be switched on or off using the relay front panel setting switch (dip switch 4). The action on negative phase sequence is to trip. The negative phase sequence pickup point is fixed at 15% of the motor FLC (Iflc). If the negative phase sequence current rises above the pick up value the relay will trip in a time determined by the curve below. The negative phase sequence protection is inhibited for motor currents of below 0.1 times and 2 times Inom. The negative phase sequence protection is automatically or manually reset as determined by dip switch 5. Phase loss will result in a trip occurring in 1.5 seconds. Secs %NPS Reset. When the relay has tripped it may be either manually or automatically reset according to the following table. Trip Reset Switch Overload Auto/man Switch 1,6 Earth fault Auto/man Switch 1,7 Locked rotor Auto/man Switch 1,7 NPS Auto/man Switch 1,7 Alarm Reset Switch Overload Auto - Undercurrent Auto - Issue 3 8/10/98 Page 11 MPR10

14 Automatic reset. When the fault condition is no longer present, for example the thermal capacity has dropped below its reset limit, the trip relay will reset allowing a restart. Manual reset. The trip condition is latched until the relay is reset by removal and re-application of the auxiliary supply or by pressing the reset button on the front panel. Note: a manual reset can only be effected if the trip condition is no longer present. Special condition reset. To effect a premature reset of an overload trip the 'Test' push button must be held down as the auxiliary power is restored Full Load Current Setting (Iflc). Determines the normal running full load current of the machine, this is set in terms of the CT ratio, thus if the CT has a primary rating of 200:1, and the machine has a FLC of 150A, Then Iflc should be set at 150/200 = t6x Setting. This setting specifies the time taken to trip at 6 times FLC, with respect to the cold characteristic curve, and therefore determines the basic thermal characteristic Normal/Factory Mode. This setting, selectable between Normal(off) or Factory (on) by use of the relay front panel setting switch ( DIP Switch 8). The functions of this are pre set, and should not be adjusted without consultation with P&B, this should be left in the Normal ( off ) position. Issue 3 8/10/98 Page 12 MPR10

15 7.3. Overcurrent Trip Inhibit. The relay can be switched to either contactor fed or circuit breaker fed through dip switch 5. In the case of contactor fed mode the MPR 10 relay trip outputs are inhibited for phase overcurrents above 7 times Iset, this is in order to provide full co-ordination between the fuse and the contactor, to ensure the fuse clears faults in excess of the contactor breaking capacity. For earth faults a one second delay is provided integral to the unit, this normally provides sufficient time for the fuse to clear any faults, at high or medium voltage however, there are a few occasions usually where impedance earthing is used, when this is not the case. In such circumstances a full co-ordination study is almost mandatory, and the following special connections may be used. L1 L2 L3 S2 P2 1S1 Supply A1 A2 P1 S1 L1 L2 L3 P2 Rstab 1S1 1S2 2S1 2S2 3S1 3S2 I3 IE I1 POWER SUPPLY TRIP ALARM MPR P1 S1 1S2 2S1 Typical earthing shown 2S2 Alternative connections for CBCT CBCT 3S1 3S2 Special CT connections for earth fault trip inhibit above 7 x Set 7.4. Setting Value Calculation. In order to ensure that protection relays form an integral part of any system, a full protection coordination study should normally be undertaken which considers both upstream and downstream equipment. Further details may be obtained by contacting P&B Engineering. 8. Relay Case. The MPR 10 is delivered in an individual case for Din rail mounting. Issue 3 8/10/98 Page 13 MPR10

16 9. Test And Maintenance. Currents may be supplied to the input transformers to test the behaviour of the relay. By switching on test currents and measuring the tripping time, the whole system can be accurately tested. All measuring input circuits of the MPR 10 are of static design and the relay functions are fully digitised. Thus, the MPR 10 has no particular demand on maintenance. 10. Technical Data Measuring Input Circuits. Rated Data Rated current, In Rated frequency, fn 1A or 5A 40-70Hz Power Consumption Current Circuits Thermal withstand For 1A Relays Half wave for 1 second for 10 seconds In = 1 A In = 5 A VA 270A 90A 30A 10A For 5A Relays Half wave 1350A for 1 second 450A for 10 seconds 150A Continuously Auxiliary Power Supply. Supply Voltage Vaux = v DC or v AC Power Consumption Quiescent Operating Approx. 4W Approx. 6W Issue 3 8/10/98 Page 14 MPR10

17 10.3. Setting Ranges And Steps. Function Parameter Setting range Step Tolerance Thermal curve Iflc t6x x In 0.5, sec 2% 1 sec 1% of setting ±1% or ±20ms under- Iu 10-50% x Iset 10% 1% of setting current Ie Ie 10-50% x In 10% In 1% of setting Thermal Current / Time Curves. The curves shown are the time/current operating characteristics for the MPR10 Thermal Overload protection. Curve 1 :Cold Curve Curve 2 :Hot Curve Overload Setting =105% Overload Setting = 105% Running From 100% FLC Hot/Cold Ratio = 50% t Multiples of FLC Issue 3 8/10/98 Page 15 MPR10

18 10.5. Output Contact Ratings. Number of relays = 2 Contacts = 1 change over contacts for trip signal. 1 change over contact for alarm. Maximum breaking capacity 250V AC / 1500VA / continuous current 5A for DC voltage: ohmic L/R = 4ms L/R = 7ms 110 V DC 0.5 A / 55 W 0.4 A / 40 W 0.2 A / 22 W 60 V DC 0.7 A / 42 W 0.5 A / 30 W 0.3 A / 17 W 24 V DC 6 A / 144 W 4.2 A / 100 W 2.5 A / 60 W Max. rated making current: mechanical life span: electrical life span: Contact material 64A(IEC65) operating cycles operating cycles at 220 V AC / 6A Silver Cadmium Oxide (AgCdO) System Data. Design standard = IEC 255-4, BS 142 Operating temperature range = 0 C to 70 C Storage temperature range = -25 C to 70 C Test Voltages to EN , EN Isolation Test = 2.5kV / 50Hz / 1 min. Impulse Test = 5kV, 1.2 / 50mS, 0.5J High frequency interference Test= 2.5kV / 1MHz Burst transient Test = 4kV / 2.5KHz, 15mS ESD Test = 8kV RFI Suppression Test = 10V/m, MHz, 1 Octave/ 3 min. EMI Suppression Test = 10V/m Mechanical Tests: Shock = IEC 41B (CO) 38, Class 1 Vibration = IEC 41B (CO) 35, Class 1 Degree of Protection = IP54 Weight = Approx. 250g. Issue 3 8/10/98 Page 16 MPR10

19 10.7. Housing. MPR 10 units are supplied in standard cases, Suitable for direct mounting on Din rail complying with BS-5584:1978. ( Top hat section ). All the terminals are situated at the top and bottom of the relay front panel, the screw terminals can accept one or two wires of up to 2.5mm 2. The unit may be sealed to prevent unauthorised adjustment, by passing a wire through the small loops moulded in the front facia, and crimping with a seal. 1S1 1S2 2S1 2S2 3S1 3S2 A1 TEST I> I>> I> In I>> In ti> ti>> A Din rail mounting: Top Hat Profile to BS5584:1978 (EN , DIN ) All dimensions are approximate and in mm Publication Changes. Form Issue 2 The auxilliary input to the MPR10 and its communication module has changed. From Issue 1 The use of a portable test case for the testing of a MPR10 is no longer required. All information subject to change without notice Publication number:- Issue 3 8/10/98 Issue 3 8/10/98 Page 17 MPR10

20 11. Order Form. QUANTITY MPR 10 Rated current 1A 1 5A 5 Optional Communication Module C PBSI Ltd Trading as P&B ENGINEERING Bell Vue Works, Boundary Street, Manchester. M12 5NG. Tel: Fax: Issue 3 8/10/98 Page 18 MPR10