The RET615 is the transformer protection and control relay of ABB's Relion 615 series, for power, unit and step-up transformers, including generator-transformer blocks. Its relatives, the RET620, RET630 and RET650, cover applications with more inputs, more control or more windings. All are configured with PCM600 and integrate IEC 61850.
What it is and where it is used
The ABB RET615 relay is the transformer protection and control relay of the Relion 615 series. ABB presents it for power, unit and step-up transformers, including generator-transformer blocks. It is common in distribution substations, in industrial plants with medium-voltage transformers and in generating stations. Three references with the same purpose appear alongside it: RET620, RET630 and RET650.
To understand the main function, see the guide on transformer differential protection 87T and the one on the transformer protection scheme.
Variants: RET615, RET620, RET630 and RET650
| Model | Application | Main difference |
|---|---|---|
| RET615 | Two-winding transformers at medium voltage | Compact, withdrawable unit; standard current-only or current-and-voltage configurations |
| RET620 | Transformers with more input, output and control needs | 620 series: more hardware and configuration flexibility on the same base |
| RET630 | Transformers with broader bay control | 630 series: freer configuration and control of several apparatus |
| RET650 | Transformers in high-voltage substations | Hitachi Energy 650 series, with predefined applications |
There are IEC and ANSI editions of the RET615. ABB states that the ANSI edition adds, for example, six setting groups, high-speed outputs and arc flash detection. What a given unit includes is read in its order code.
Main functions
| Function | ANSI | What it provides |
|---|---|---|
| Transformer differential with stabilized and instantaneous stage | 87T | Main protection against internal faults (guide) |
| Restricted earth fault | 87N | Earth faults near the neutral (guide) |
| Phase and ground overcurrent on both windings | 50/51, 50N/51N | Backup for uncleared external faults (guide) |
| Thermal overload | 49 | Sustained overload (guide) |
| Breaker failure | 50BF | Local backup (guide) |
| Overexcitation and voltage (configurations with voltage) | 24, 27, 59 | Abnormal system conditions |
The differential includes harmonic blocking for inrush current and overexcitation. The transformer’s mechanical protections (Buchholz, sudden pressure) reach the relay through binary inputs.
Communications and integration
ABB states that the RET615 supports IEC 61850 editions 1 and 2, with GOOSE messages and PRP and HSR redundancy, as well as Modbus, DNP3 and IEC 60870-5-103. Engineering, settings and SCL files are handled with PCM600; there is also a web interface on the relay itself for viewing.
The eight standard configurations of the RET615 (product guide 5.0 FP1)
The RET615 product guide (version 5.0 FP1, revision M, IEC edition) describes eight standard configurations, A to H. All are transformer differential; what changes is the type of restricted earth fault and whether there is voltage measurement and protection:
| Configuration | Restricted earth fault | Voltage |
|---|---|---|
| A | Low impedance, high-voltage side (HV) | No |
| B | Low impedance, low-voltage side (LV) | No |
| C | High impedance, HV side | No |
| D | High impedance, LV side | No |
| E | Low impedance, HV side | Voltage protection and measurements |
| F | Low impedance, LV side | Voltage protection and measurements |
| G | High impedance, HV side | Voltage protection and measurements |
| H | High impedance, LV side | Voltage protection and measurements |
The choice between low and high impedance depends on how the neutral current transformers are connected and on the criteria of your study; see high-impedance differential protection. In all configurations the relay includes phase overcurrent on both windings, negative sequence, a two-time-constant thermal model and tap changer position indication.
The factory signal routing can be altered with the signal matrix or with the application configuration tool of PCM600, which allows building multi-layer logic with timers and flip-flops. The relay leaves the factory with the default connections described in the functional diagrams of each configuration.
Temperature, tap changer and other inputs
- Optional RTD and mA. In configurations with the optional module, ABB describes inputs to measure top and bottom oil temperature, ambient temperature and, in dry-type transformers with Pt-100 sensors, thermal protection. That measurement extends the relay’s thermal overload function.
- Tap changer position. An RTD input can be used as a direct resistance measurement for the on-load tap changer position, or the position is obtained through an mA transducer. These values can be sent to other devices through analog GOOSE messages.
- Voltage regulation. In the guide’s application example, automatic regulation of the tap changer is done by another relay of the series (REU615), while the RET615 is dedicated to protection and oil monitoring. In other words, the RET615 does not replace the voltage regulator. See parallel transformers with tap changer.
- Time synchronization: IEEE 1588 v2, SNTP and IRIG-B. User interface: local display, user management and web browser. Communication: IEC 61850 with Edition 2, IEC 61850-9-2 LE process bus, IEC 60870-5-103, Modbus and DNP3, with copper Ethernet (RJ45) or fiber (LC).
RET630: what can be stated
For the RET630, the ABB brochure in Spanish that we consulted indicates that IEC 61850 communication covers both vertical (with the control system) and horizontal (between devices, with GOOSE messages) communication. It also indicates that time synchronization can be done over Ethernet with SNTP or over a separate bus with IRIG-B. The specific functions, inputs and licenses depend on the product version and its guide; we leave them out of this page until they are checked against the guide for the version you have.
Common mistakes when applying a transformer relay
- Applying the vector group setting without considering that the compensation is done inside the relay and not with the current transformers.
- Leaving the temperature inputs unconnected and assuming the thermal model already incorporates the real oil measurement.
- Mixing up editions: the ANSI edition has its own standard configurations (two in the guide consulted) and its own product guide.
- Forgetting the trip and blocking of the mechanical protections; see transformer mechanical protections.
Frequently asked technical questions
- Which manual corresponds to the RET615? ABB separates the product guide, application manual and technical manual by version and by edition (IEC or ANSI). Use the one for the version of your relay.
- Differential trip on energization: it usually comes from the vector group compensation, the CT ratio or the harmonic blocking. We explain it in 87T trip without internal fault and in transformer trip on energization.
- PCM600 connectivity package: if it does not match the relay version, errors appear when reading or writing.
- CT polarity: a differential with one reversed CT measures differential current under normal load.
How we help
At Tiza Group we remotely configure and review RET615, RET620, RET630 and RET650 relays with PCM600: configuration, differential settings, IEC 61850 and disturbance records, based on the study and the approved settings. See the scope in remote configuration of Relion relays. If your transformer tripped and it is not clear why, we quote the trip analysis. You can also write to us through contact.
Related guides
- Relion 615 relays
- Transformer differential protection 87T
- Transformer protection scheme
- Transformer mechanical protections 63 and 26
- SEL-487E relay
- ABB and Hitachi Energy PCM600, IET600 and ITT600 software
- ABB UZ, UC and VUC tap changer (Hitachi Energy)
References
- IEEE C37.2, device numbers; IEEE C37.91, transformer protection.
- IEC 61850 (series) and IEC 62439-3 (PRP and HSR).
- ABB, RET615 (IEC and ANSI) and RET620 product guides; Hitachi Energy, RET650 product page.
Frequently asked questions
What is the RET615 relay used for?
To protect, control, measure and supervise power, unit and step-up transformers, including generator-transformer blocks. Its main function is multi-slope transformer differential protection with an instantaneous stage, complemented by backup overcurrent on both windings, restricted earth fault, thermal overload and breaker failure.
What software does the RET615 use and where is the manual?
It is configured with PCM600, ABB's tool for Relion relays, with the connectivity package for the relay version. ABB publishes the product guide, the application manual and the technical manual for each version in its library, in IEC and ANSI editions.
Is the RET650 from ABB or from Hitachi Energy?
The 650 series is now marketed by Hitachi Energy, which acquired ABB's power grids business; the 615 and 620 series remain with ABB. Both use PCM600, but each device requires its own connectivity package.