The RET670 and REB670 are relays of the Hitachi Energy Relion 670 series (the series started at ABB): the RET670 protects, controls and monitors transformers and reactors, and the REB670 protects busbars with up to six zones from medium to extra-high voltage. The REB500 is the distributed busbar protection of the same family, with bay units for substations of 2 to 60 bays.
What it is and where it is used
The RET670 and the REB670 belong to the Relion 670 series from Hitachi Energy. The series started at ABB and is now marketed by Hitachi Energy, which acquired ABB’s grid business; for that reason in the field you find them under both brands, and they are also named “RET670 ABB”. They are relays for high- and extra-high-voltage substations, although the REB670 covers from medium voltage.
- The RET670 protects, controls and monitors power transformers, autotransformers, phase-shifting transformers and shunt reactors.
- The REB670 protects busbars, T-connections and mesh corners in up to six zones.
- The REB500 is the distributed busbar protection of the Relion family.
For the principle of each protection, see transformer differential protection 87T and bus differential protection 87B.
RET670, REB670 and REB500 variants
| Model | Application | Main difference |
|---|---|---|
| RET670 | Two- and three-winding transformers, autotransformers, phase shifters, reactors | Differential with automatic ratio and vector group compensation, no interposing CTs; can carry two differential functions |
| REB670 | Single, double and triple busbars, with or without transfer, double breaker and breaker-and-a-half | Centralized protection, up to six zones |
| REB500 | Busbars of substations of 2 to 60 bays | Distributed, up to 32 differential zones, independent disconnector check zone |
Main functions
| Function | ANSI | Device | What it adds |
|---|---|---|---|
| Transformer differential | 87T | RET670 | Main transformer protection (guide) |
| Restricted ground fault | 87N | RET670 | Ground faults near the neutral (guide) |
| Backup overcurrent, thermal overload | 50/51, 49 | RET670 | Backup and overload (49) |
| Overexcitation | 24 | RET670 | High volts-per-hertz ratio |
| Low-impedance bus differential | 87B | REB670, REB500 | Fast clearing of bus faults (guide) |
| Breaker failure | 50BF | REB670, REB500 | Zone trip if a breaker does not open (guide) |
The RET670 is designed to operate over a wide frequency range, useful during generator start-up and shutdown, and includes local and remote control functions for the equipment on all sides of the transformer. The REB670 clears phase-to-phase and phase-to-ground faults in solidly grounded or low-impedance systems, and multiphase faults in isolated or high-impedance systems. The REB500 keeps the measurement correct even with current transformer saturation.
Communications and integration
The Relion series is designed on IEC 61850: GOOSE messages, MMS and, depending on the version, process bus. The REB500 supports IEC 61850 and Hitachi Energy highlights its cybersecurity architecture (TLS, per-service certificates, VLAN and user management with Active Directory). The RET670 and REB670 are configured with PCM600; for the REB500, the engineering tool depends on the installed version. See IEC 61850 SCL files.
What the RET670 version 2.2 brings
The RET670 version 2.2 product guide (first edition July 2017; revision J, May 2019, corresponds to version 2.2.3) describes:
- Low-impedance differential with second-harmonic and waveform-block restraint, and fifth-harmonic restraint against overexcitation, with up to six restraint CT inputs.
- Sensitive differential function for low-level internal faults, based on negative-sequence magnitude and directional comparison.
- Several low-impedance restricted ground fault functions, and a high-impedance differential function that serves REF, autotransformers, reactors, buses and generators.
- Backup: distance protection, positive-, negative- and zero-sequence overcurrent (optionally directional), thermal overload, overexcitation, voltage, frequency, breaker failure for each transformer breaker, out-of-step and synchrocheck.
- Control: optional voltage and tap changer package (automatic voltage regulation), with interlocks.
- Preconfigured packages: A10 (transformer backup), A25 (voltage and tap changer control), B30 (two-winding differential, one or several breakers) and B40 (three-winding differential, several breakers). According to the guide’s diagrams, B30 uses 12 analog channels (9 current and 3 voltage), expandable to 24 with an additional module; B40, 24.
- Binary inputs with stabilization against DC disturbances, intended for Buchholz, pressure and temperature signals (see Buchholz trip or sudden pressure).
The detail of each package changes with the version and the order reference; always confirm against the guide of the installed version.
Version 2.2 of the 670 series
Hitachi Energy released version 2.2 of the Relion 670 series on December 21, 2018 (release note 1MRG033151), for the REB, REC, RED, REG, REL, RER, RES and RET670, and new orders of that version are delivered with that update. Among the new features:
- Support for several Ethernet ports, the HSR redundancy method and precision time synchronization according to the IEC/IEEE 61850-9-3 profile.
- Sampled values IEC/UCA 61850-9-2LE on all 670 products (the RET670 supports up to eight merging units, according to its guide). See IEC 61850 sampled values and process bus.
- Current and voltage delta supervision, with vector shift calculation, and harmonic monitoring up to the fifth with total distortion.
- In the RET670, a differential protection for phase-shifting transformers that only needs external CTs and VTs and adapts to the phase angle and voltage ratio.
- PCM600 2.8 and connectivity package 3.2.5 are required for the 670 series, which supports 2.2 and earlier.
Two busbar protection philosophies
The REB670 is a centralized protection: the bay currents arrive at a single device, so the size of substation it can cover depends on how many current inputs its configuration admits; confirm that limit in the guide of the version. The REB500 uses bay units and a central unit, and covers 2 to 60 bays. The choice between them depends on the topology, the planned expansion and the cybersecurity requirements. For the principle of each scheme, see busbar protection schemes. See also SIPROTEC 7SS85 and 7SS52 relays.
Frequently asked technical questions
- 87T trip without an internal fault: energization, overexcitation or a vector group compensation error. See 87T trip without an internal fault.
- Disconnector replica in the bus protection: if a disconnector position arrives wrong, the zone is poorly defined; that is why the check zone exists.
- PCM600 connectivity package: it must match the IED version.
- Transformers with two zones: a RET670 can carry two differential functions, for example for a transformer with its bus or with a reactor; each zone needs its own CTs at all its limits.
- REB500 with new bays: when the substation is expanded, bay units are added and the central unit configuration and the disconnector replica are updated.
How we help
At Tiza Group we configure Relion relays remotely, worldwide, with a backup before and after the change. See remote configuration of Hitachi Energy and ABB Relion relays and remote relay configuration. If the transformer or the bus has already tripped and it is not clear why, we quote the event analysis in trip review, or write to us through contact.
Related guides
- Transformer protection scheme
- Busbar protection schemes
- Bus differential protection 87B
- Breaker-and-a-half configuration
- Hitachi Energy REL670 relay
- SEL-487E relay
- ABB and Hitachi Energy software PCM600, IET600 and ITT600
- ABB REC670, REC650 and REC615 bay controller
- SIPROTEC 7SS85 and 7SS52 Busbar Protection Relays
References
- IEEE C37.2, device function numbers for power systems.
- IEEE C37.91, guide for protecting power transformers; IEEE C37.234, guide for protective relay applications to power system buses.
- Hitachi Energy, product pages of the RET670, REB670 and REB500.
Frequently asked questions
Is the RET670 from ABB or from Hitachi Energy?
Today the Relion 670 series, which includes the RET670 and REB670, is marketed by Hitachi Energy, which acquired ABB's power grids business. In the field you find equipment with either brand; the platform and the PCM600 tool are the same.
What is the difference between the REB670 and the REB500?
The REB670 is a centralized busbar protection: one IED that receives the currents of the bays in the zone. The REB500 is distributed: bay units in each cubicle connected to a central unit, and it scales from 2 to 60 bays with up to 32 differential zones. The choice depends on the size and configuration of the substation.
Where is the REB500 technical manual?
Hitachi Energy publishes the technical, application and operation manuals of the REB500 and REB670 in the resources section of each product. They explain the functions; the settings and the disconnector replica depend on the actual configuration of the substation.