ABB REL670 distance protection and troubleshooting

ABB REL670 distance protection and troubleshooting

Introduction: Why can't we just look at the fixed value for distance protection and obstacle removal

ABB REL670 is a line distance protection IED in the RELION 670 series, aimed at transmission lines and secondary transmission lines, providing multi segment distance protection, directional overcurrent, ground fault protection, reclosing, synchronous inspection, fault location, disturbance recording, and IEC 61850 communication functions. When there is a "distance protection misoperation", "out of zone fault tripping", "unsuccessful reclosing", or "large fault distance measurement deviation" on site, many engineers' first reaction is to check the set value, but the real cause is often CT/VT polarity, voltage circuit, direction setting, load intrusion, power swing lockout, or communication channel.

The distance protection of REL670 adopts a full scheme measurement, with each segment containing three phase to ground circuits and three phase to phase circuits. Quadrilateral and Mho characteristics are optional, with a maximum of five segments. It supports load intrusion, power swing detection, fault phase selection, adaptive load compensation, fault location, and single-phase reclosing. When troubleshooting, the order of "checking the analog input and direction first, then checking the distance element and phase selection, and finally emphasizing the closing, recording, and communication" should be followed, rather than repeatedly modifying the impedance setting.

First check the analog input: CT/VT direction is wrong, distance protection must be wrong

The analog input of REL670 is connected through the transformer input module TRM, sampled by ADM, and preprocessed by SMAI. Distance protection uses three-phase current, three-phase voltage, and zero sequence quantity, and all fixed values are represented as primary values. Therefore, CT, VT ratio, and polarity settings are the basis.

CTStarPoint setting is the top cause of directional errors. REL670 regulation: Positive current and positive power indicate the flow towards the protected object, and the forward direction always points towards the protected object. If the CT star point is connected incorrectly, CTStarPoint should be set to ToObject but set to FromObject, or vice versa, the directional component will classify faults inside the area as outside the area and faults outside the area as inside the area. On site performance: no jumping due to forward direction fault, false jumping due to reverse direction fault; Or start the distance segment but lock the direction. During troubleshooting, CTStarPoint, CT ratio, and VT ratio should be checked one by one in the SMAI or TRM parameters, and compared with the CT nameplate, secondary wiring diagram, and star point grounding position inside the cabinet item by item.

The voltage circuit cannot only be checked for voltage. The secondary fuse of VT, tripping of air switch, loose terminals, reversed phase sequence, and unconnected neutral point can all cause impedance distortion in distance component measurement. The fuse failure monitoring of REL670 can detect voltage circuit faults through negative sequence or voltage/current difference algorithms, and lock the voltage dependent protection after action. If the fuse fails, the VT secondary fuse, air switch auxiliary contacts, and voltage terminals should be checked first, rather than adjusting the distance setting. Reverse voltage phase sequence can also cause errors in the selection of directional components and fault phases. A phase table should be used on site to verify the correspondence between Uab, Ubc, Uca and Ia, Ib, Ic.

CT secondary cannot open circuit, VT secondary cannot short circuit. Check the CT terminal short-circuit, the automatic short-circuit contact of the withdrawable unit, the VT secondary fuse, and the grounding. For newly put into operation or renovated intervals, a secondary injection test should be conducted to verify the starting, direction, and tripping outlet of each distance component.

Selection of Distance Components and Characteristics: Quadrilateral, Mho, and Load Intrusion

REL670 provides quadrilateral characteristic distance segments, Mho characteristic distance segments, series compensation line quadrilateral distance segments, etc. The quadrilateral characteristic is suitable for situations where independent setting of resistance and reactance ranges is required, while the Mho characteristic is suitable as a backup protection, especially in high load, multi terminal lines. When troubleshooting on site, it is necessary to first confirm which characteristic is actually in operation, and then check the corresponding set value.

Common issues with quadrilateral distance segments. ZMQPDIS is used for the first paragraph, and ZMQAPDIS is used for the second to fifth paragraphs. Each segment has positive sequence reactance X1, positive sequence resistance R1, zero sequence reactance X0, zero sequence resistance R0, phase to phase fault resistance RFPP, phase to ground fault resistance RFPE, minimum operating current IMinOpPE/IMinOpPP/IMinOpIN, etc. If there is a fault outside the area that exceeds the level, it is necessary to check whether the RFPE/RFPP is too large, whether the load intrusion characteristics have not been activated, and whether the time difference is sufficient. If the high resistance grounding fault in the area refuses to operate, check whether the RFPE is too small, whether the zero sequence compensation coefficient KN is consistent with the line parameters, and whether the minimum operating current is too high.

Common issues with Mho distance range. ZMHPDIS uses positive sequence polarized memory voltage, with directionality dependent on ZDRDIR. Mho circle relies on memory voltage to maintain direction judgment during near end three-phase faults; The memory voltage is generally maintained for 100ms. If the direction of the near end three-phase fault is reversed, check whether the ArgDir and ArgNegRes settings of ZDRDIR have been changed, and whether the polarization voltage meets the minimum threshold. The load intrusion of Mho characteristics is coordinated with FMPSPDIS. If the load intrusion is not configured correctly, the overloaded line may malfunction or refuse to operate.

Load intrusion is not a 'fault', but it will change the action boundary. When the transmission power of the line is high, the load impedance may enter the distance range action zone. REL670 uses the load intrusion characteristics of FDPSPDIS or FMPSPDIS to set blind spots in the resistance direction, avoiding the load impedance from being treated as a fault impedance. If there is a "distance segment start when the load increases" on site, the load intrusion resistance RLdFw/RLdRv and load angle ArgLd should be checked to see if they match the actual load, rather than simply increasing the distance segment resistance setting.

Directional and phase selection: hidden reasons for out of zone fault escalation

The direction determination of distance protection is completed by ZDRDIR, and the phase selection is completed by FDPSPDIS or FMPSPDIS. The two interact with the distance segment through binary encoded signals: STCND is the loop enable for the distance segment, and DIRCND is the directional condition. If these two signals are connected incorrectly or configured incorrectly, the distance segment may not move at all or move in the wrong direction.

Reverse direction investigation. First check CTStarPoint, then check the polarity setting of ZDRDIR, and finally check the phase sequence of voltage and current. For double circuit lines or parallel lines on the same tower, it is also necessary to check the zero sequence mutual inductance compensation and current reverse logic. If there is a fault outside the area and the local distance segment starts but the opposite side does not jump, the communication channel and enable/lock logic should be checked, rather than just changing the time setting.

Troubleshooting of phase selection errors. The STCNDZ output of FDPSPDIS is used for quadrilateral distance segments, while STCNDLE is used for load only intrusion conditions. If the phase selection classifies a single-phase grounding fault as a three-phase fault, the recloser will trip according to the three-phase, causing the single-phase recloser to fail. The zero sequence current threshold INRelease PE, INBlockPP, negative sequence voltage threshold U2MinOp, positive sequence voltage threshold U1MinOP, and other settings should be checked, and combined with waveform recording to view the current, voltage, and sequence components before and after the fault.

Locking of power swing, load intrusion, and distance protection

REL670's ZMRPSB is used for power swing detection, while ZMRPSL is used for power swing logic. When the power swings, the impedance trajectory will pass through the action zone of the distance range. If it is not locked, the distance protection may malfunction. When there is a "distance protection trip during system oscillation" on site, it is necessary to check whether ZMRPSB is activated, whether the internal and external quadrilateral boundaries, tP1/tP2/tW/tH time settings are reasonable, and whether ZMRPSL's locking and permission logic is correct.

Power swing detection relies on impedance change speed. If tP1 is set too small, the fault may be mistaken for swing; If tP2 is set too large, it may be considered a malfunction due to swinging. The impedance trajectory and current change rate in the disturbance recording should be combined for verification. For heavy-duty lines, load intrusion and power swing may coexist, and the load intrusion characteristics of FDPSPDIS and the swing boundary of ZMRPSB should be checked separately to avoid mutual interference between the two.

Recloser and fault location: "result verification" after troubleshooting

REL670 supports SMBRREC automatic reclosing up to five times, supports single-phase, two-phase, and three-phase reclosing, and can be synchronized with SESRSYN for inspection. If the reclosing is unsuccessful, one should first distinguish between "protection not issuing reclosing command", "reclosing locked", "circuit breaker not closed", and "tripping again after closing".

Common reasons for unsuccessful reclosing. Check if CBREADY meets the requirements, if CBPOS was closed before the fault, if INHIBIT was locked by external signals, if SYNC is met within tSync, and if the reclosing method matches the fault type. When a single-phase fault occurs, if the protection triggers a three-phase trip, the reclosing will not operate in a single-phase manner; The program settings and phase selection output of SMPPTRC should be checked. After reclosing and tripping again, the fault recording should be checked to determine whether it is a permanent fault or a reclosing fault.

Troubleshooting for large deviations in fault location. LMBRFLO calculates fault distance based on impedance measurement, which requires parameters such as positive/zero sequence impedance of the line, line length, impedance of both sides of the power supply, and zero sequence mutual inductance. If the distance measurement deviation is large, it is necessary to check whether the line parameters are consistent with the actual measurement, whether the CT/VT ratio is correct, and whether the fault type and fault phase are identified correctly. For double circuit lines, setting the zero sequence mutual inductance Z0M incorrectly will significantly affect the distance measurement results. The fault location results should be compared with the voltage and current waveforms in the waveform recording and the inspection results of the fault point, rather than just looking at the single distance measurement values.

Communication, event recording, and hardware replacement

REL670 supports communication such as IEC 61850-8-1, GOOSE, DNP3, IEC 60870-5-103, LON, SPA, etc. The troubleshooting related to distance protection and communication includes: GOOSE disconnection causing the signal to not be received, inconsistent event times at the station control layer, failed upload of disturbed files, and abnormal switching of redundant channels.

GOOSE has broken its chain. First check the fiber optic cables, switch ports, OEM module indicator lights, and then check the GOOSE dataset APPID、 Subscription relationship and network configuration. If GOOSE is disconnected but the protection can still operate, it indicates that the distance protection itself is normal, and the problem lies in the communication configuration or switch.

Events and recording. The disturbance report of REL670 includes event list, indication, event record, trip value record, disturbance record, and fault location. When troubleshooting, the event record should be read first to confirm the timing of protection activation, direction judgment, trip exit, and reclosing commands; Let's take a closer look at the analog and switch values in the disturbance recording. If the event time is inconsistent with the station control layer, the time synchronization source and SynchAccLevel settings should be checked.

Hardware replacement. After replacing modules such as TRM, ADM, NUM, PSM, BIM, BOM, IOM, SLM, OEM, LDCM, etc., it is necessary to verify whether the configuration and parameters have been re downloaded, check SMAI channel mapping, CT/VT ratio, binary input-output mapping, and communication configuration. After replacing the motherboard or NUM, the firmware version, configuration file, and cycle time should be rechecked. For distance protection, a second injection test must be conducted after replacing the TRM or ADM to verify the direction and action boundary of each distance component.

On site troubleshooting checklist: from "phenomenon" to "root cause"

Phenomenon 1: The positive direction fault does not jump. Check CTStarPoint, VT voltage, ZDRDIR direction, STCND/DIRCND connection, distance range switching, minimum operating current RFPE/RFPP。

Phenomenon 2: Wrong tripping due to reverse direction fault. Check CT polarity CTStarPoint、 Direction setting, parallel line zero sequence mutual inductance compensation, power swing locking.

Phenomenon 3: Out of zone faults exceeding the level. Check time difference, load intrusion RFPE/RFPP、 Communication enabled/locked logic, whether ZMRPSB is erroneously locked.

Phenomenon 4: Single phase fault and three-phase tripping. Check FDPSPDIS phase selection, SMPPTRC program, single-phase reclosing mode, and three-phase trip input.

Phenomenon 5: Failed reclosing. Check CBREADY, CBPOS, INHIBIT, SYNC, tSync, reclosing frequency and method.

Phenomenon 6: There is a large deviation in fault distance measurement. Check the line parameters, CT/VT ratio, zero sequence mutual inductance, fault type identification, and impedance of both sides of the power supply.

Phenomenon 7: Communication abnormalities. Check the number and time synchronization of fiber optic/electrical ports, OEM/SLM modules, GOOSE dataset, IEC 61850 clients.