A relay without documented settings is a relay that nobody can say what it does. The settings can almost always be recovered by reading them from the device with the manufacturer's software or, in electromechanical relays, by inspection and testing. Recovering them is only half of it: they must be validated against the current installation and a coordination study, documented and kept in controlled copies. What must not be done is reset the relay to factory defaults to "start from scratch", because the only evidence is erased.
A more common problem than it seems
In many plants and substations there is at least one relay for which nobody has the settings file. The causes repeat:
- The contractor who commissioned it delivered a paper report or nothing.
- The coordination study was lost or never existed.
- Someone changed settings after a trip and did not record it.
- The relay was replaced by another and the settings were “copied” by hand.
- The software and cable to connect to that model are no longer available.
While there are no faults, nobody notices. The problem appears when the relay trips for no reason, when it does not trip and the utility clears the fault leaving the plant without power, when the utility asks for the settings to approve a connection, or when the device has to be replaced. See nuisance trips.
What is recovered and how
A modern digital relay stores much more than the protection settings:
| Part of the configuration | Why it matters |
|---|---|
| Protection settings | Pickups, times, curves and setting groups |
| CT and VT ratios | If they do not match what is installed, all settings are shifted |
| Programmable logic | Blocks, interlocks, transfer trips, reclosing |
| Inputs and outputs | Which contact trips which breaker, which signal reaches which input |
| Event recording and oscillography | What is recorded and on which trigger |
| Communications | Addresses, protocols, data maps, IEC 61850 files |
| Time and synchronization | Without correct time, events cannot be compared |
Digital relays. The configuration is read from the device with the manufacturer’s software: AcSELerator QuickSet for SEL, PCM600 for ABB, DIGSI for Siemens, EnerVista for GE Multilin, MiCOM S1 or Easergy Studio for Schneider, among others. The real difficulties are practical: software and firmware versions that do not match, ports and cables of old models, unknown passwords and in-service equipment that cannot be put at risk. In IEC 61850 substations, the relay file (CID) and the substation file (SCD) are also part of the configuration. See IEC 61850 SCL files and Siemens DIGSI software.
Electromechanical relays. They have no file: the settings are in the taps, dials and springs. They are recorded by inspection and confirmed by testing the real characteristic with secondary injection, because mechanical wear means the relay does not always operate where its dials say. See replacing electromechanical relays with digital ones.
Validate: what was read is not necessarily right
Recovering the settings answers “what does the relay have”. The important question is “what should it have”. For that, they are compared with:
- The current installation: installed CT and VT ratios, transformer rating and connection, motors, cables.
- A current coordination study, or a new one if none exists or the installation changed.
- The utility’s requirements at the point of connection.
- Trip records: a relay that tripped several times with no apparent fault usually has a setting that does not fit.
It is common to find factory settings never changed, CT ratios that do not match the nameplates, functions enabled but unused and logic from a previous project. See protection coordination and setting criteria.
Document and do not lose them again
- Reading. Complete device configuration, changing nothing
- Validation. Comparison with the installation, the study and the utility
- Correction. New settings where needed, approved before loading
- Testing. Secondary injection of the functions and the trip circuit
- Archive. Native file, readable report, version, date and owner
The minimum documentation for each relay includes the native file of the software (so it can be reloaded), a readable report of settings and logic, the firmware version, the date, who changed it and why, and the test report. Copies are kept outside the relay and outside any single person’s computer, with simple version control. Every later change, however small, produces a new version.
The file is not enough: firmware and version control
A saved configuration only makes sense together with the relay model and the firmware version it was made for. The report of working group P6 of the IEEE PES communications and cybersecurity committee on Ethernet networks for protection and control (2017) puts it this way. Without clear and reliably backed-up configuration files it is impossible to diagnose an installation or quickly replace a failed device. Since a single incorrect setting can affect critical functions, it recommends a strictly controlled process. This process is used to prepare and track the settings files and the associated hardware and firmware versions. It also calls for a protected and controlled archive where maintenance staff always find the latest version. The same report notes that in North America the retention and recovery of these files is codified in the NERC CIP regulations. These regulations are not international, but they serve as a guide for a recovery plan. To go further: case of settings lost after a relay swap with no backup. See also periodic maintenance of protection relays.
The IEEE C37.233 protection testing guide, in the summary its authors published on the 2009 edition, adds a practical criterion. In a numerical relay each hardware or software version can be a different type, and a firmware update is treated as testing a new type. If a complete type test already exists, a limited program may be enough as long as it verifies two things. The first is that the new or modified function works properly. The second is that no other function is degraded. That is why the installed firmware is part of each relay’s record, not an incidental datum.
In IEC 61850 substations there is an additional point. Amendment 1 of IEC 61850-6 states that the revision history of a file is optional and describes the changes to the file itself. The history of an SCD is, in principle, independent of that of the ICD or IID files it is based on. Even so, it can note in a comment which version of an IID was incorporated into the project. It is worth always noting it. Otherwise, when reconstructing the history of a relay, you cannot tell which version of its description the current SCD was generated from.
The test report also serves as an archive. The C37.233 guide points out that documenting the system’s field performance serves as a baseline to evaluate its future behavior, both in maintenance tests and after a real trip.
When it is urgent
Some situations cannot wait. A relay tripped with no apparent fault and was re-energized without knowing why. A plant expansion or a new transformer is added downstream. The CT ratios change. The utility asks to review coordination at the point of connection, or own generation is connected. In all those cases, unknown settings can leave a fault uncleared or take the whole plant out of service. Recovering and validating them is the first step of any change.
How we help
We recover, validate and document your relay settings remotely: we connect with you to the device, read the complete configuration, compare it with your installation and the study, correct what is needed and deliver the files and a report per relay. We work with the main brands, on relays in plants and in medium-, high- and extra-high-voltage substations. If there is no study, we make it with our protection coordination team; in Colombia, or elsewhere on request, we also test on site. See remote relay configuration and write to us with the brand and model of your relays.
Related guides
- Protective relays
- Protection coordination and setting criteria
- Medium-voltage service entrance relay
- Replacing electromechanical relays with digital ones
- Nuisance trips
- IEC 61850 SCL files
- Event report and sequence of events
- Is remote relay configuration safe?
- Case: settings lost after a relay swap with no backup
- Periodic Maintenance of Protection Relays
References
- IEEE C37.2, Electrical Power System Device Function Numbers.
- IEC 61850-6, configuration of substation automation systems (SCL).
- IEEE C37.233, Guide for Power System Protection Testing.
- IEEE PES PSCCC, working group P6: Application of Ethernet Networking Devices Used for Protection and Control Applications in Electric Power Substations (report, 2017).
- IEC 61850-6:2009/AMD1:2018, history (Header) of SCL files.
Frequently asked questions
How do I recover the settings of a relay if I do not have the file?
In a digital relay, by connecting to it with the manufacturer's software and reading the complete configuration: protection settings, logic, inputs and outputs, events and communications. In an electromechanical relay, by recording the taps and dials and testing its characteristic with secondary injection. In both cases, the result is saved and compared with a study before accepting it.
What do I do if the relay has a password and nobody knows it?
Do not reset the device to factory values without first trying to read it: on many models the reset erases the settings. Each manufacturer has a procedure to recover access, which sometimes requires physical access to the device or manufacturer support. Plan it with the circuit out of service or with backup protection.
Is reading the relay settings enough?
No. Reading says what the relay has, not whether it is right. You must check that the settings match the installed CTs and VTs, the protected equipment and the coordination with neighboring protection and with the utility. If the installation has changed since the relay was set, they most likely need correcting.