A good substation automation system (SAS) specification defines functions and results, not brands: architecture and levels, availability and redundancy, protocols inside the substation and to the control center, signal list, time synchronization, cybersecurity, FAT and SAT, documentation and the configuration files to be delivered. What the tender does not require, the supplier does not include.
Why the specification decides the outcome
In an automation project, most commissioning problems originate in the specification: signals nobody asked for, redundancy nobody planned, tests that were not in the scope, configuration files the contractor has no obligation to deliver. What the tender does not require, the supplier does not price; and what is not priced is argued about on site. In an existing substation, the tender for a SAS retrofit adds the survey of what is installed and the coexistence with the old system.
CIGRE devoted its Technical Brochure 329, Guidelines for specification and evaluation of substation automation systems, to this subject, with the aim of helping prepare specifications for substation automation systems and compare the bids. This guide summarizes, at a general level, what a tender should cover; the final text depends on each project and on the utility.
What the tender must define
| Topic | What to define | Typical error if missing |
|---|---|---|
| Scope and boundaries | Which bays, which equipment, where the SAS ends and SCADA or the DCS begins | Signals left «between two contracts» |
| Architecture | Process, bay and station levels; station bus and, if applicable, process bus | Bids that cannot be compared |
| Functions | Protection, control, interlocking, sequences, recording, metering, per bay | Implicit functions nobody included |
| Availability and redundancy | Which single failure the system must tolerate: network, gateway, HMI, clock | A single point of failure that blinds the control center |
| Protocols | IEC 61850 inside the substation, required edition; protocol and profile to each control center | Unplanned gateways, incompatible editions |
| Signals | Signal list or, at least, the template per bay type | Incomplete lists that grow on site |
| Time | Time source, synchronization protocol and required accuracy | Scrambled sequences of events |
| Cybersecurity | Requirements for access, segmentation, logging, patching and hardening | Equipment installed with no way to comply with the owner’s policy |
| Environment and compatibility | IEC 61850-3 or IEEE 1613 requirements for network and station equipment | Office switches or computers in the substation |
| Testing | Content of the FAT, SAT and point-to-point tests, and who witnesses them | Tests cut short on site for lack of time |
| Documentation and files | What is delivered, in which format and with which version | The owner cannot extend the system without the original supplier |
| Training and support | For operation and for engineering, and the warranty period | Total dependence on the contractor |
Architecture, redundancy and network
The specification sets the levels and the failure each one must tolerate. Writing «redundant system» is not enough: it has to say what happens if a switch, a gateway, the HMI or the clock fails, and how quickly communication recovers. For the substation network, that translates into the topology, the redundancy protocol (for example PRP or HSR) and traffic separation. The technical basis is in substation communication network.
Protocols and engineering
For IEC 61850 it is worth requiring:
- the required edition and how coexistence with devices of another edition will be handled, according to IEC 61850 Edition 1, 2 and 2.1;
- IED conformance certificates per IEC 61850-10 and their conformance statements;
- the use of GOOSE for interlocking or tripping, if desired;
- the SCD as a deliverable, together with the engineering tool and who will hold its license.
Toward the control center, the protocol and its profile (data types, events, synchronization, link redundancy) are normally set by the utility. The specification transcribes them and defines who does the mapping in the gateway.
Cybersecurity
The specification must ask for verifiable requirements, not statements: individual user authentication, roles, security event logging, disabled ports and services, segmentation between the substation network and the outside, and the way updates are applied. IEC 62443 (ISA/IEC 62443) gives the framework for the system and its components, and IEC 62351 for the protocols. In North America the owner’s NERC CIP obligations also shape these requirements. We develop the subject in IEC 62443 in substations.
FAT and SAT
The tender defines the content of the tests and their acceptance criteria:
- 01Type and routine testsCertificates for each device according to its standard
- 02System FATIntegrated system at the factory: functions, communications, HMI, gateway and redundancy
- 03SATInstalled system, with its final wiring and network
- 04Point-to-point testsEvery signal from the yard to the HMI and the control center
- 05Commissioning and energizationOn-load tests and final verification before operation
Each stage must have a procedure approved before it starts, with acceptance criteria and a list of who approves the results. The applicable standards (IEC 61850-4, IEC 62381 as a model, CIGRE TB 637) are in standards for commissioning, FAT and SAT, and the on-site process in substation commissioning.
Documentation and files to be delivered
Require explicitly:
- the final SCD and the files of each IED;
- settings and logic of relays and controllers, in native format and in a readable format;
- gateway, HMI and network configuration;
- the final signal list;
- updated as-built drawings;
- approved test records.
And define who maintains that information afterwards: IED and SCD configuration management keeps the system from going out of date with the first change.
How to evaluate the bids
A point-by-point compliance table, with each requirement of the tender and the bidder’s answer, allows bids to be compared objectively. It is also worth asking for the proposed architecture as a diagram, the equipment list with its certificates and experience in similar integrations.
We help you specify and execute
At Tiza Group we configure and test automation systems in medium, high and extra-high voltage substations and in industry, and we know first-hand what fails when the specification falls short. For secondary engineering and the specification, see secondary engineering; for on-site integration, control, protection and communications configuration, in Colombia, or elsewhere on request.
Related guides
- Standards for commissioning, FAT and SAT testing
- Substation communication network
- Substation signal list
- IEC 62443 in substations
- IEC 61850-3 and IEEE 1613
- Top-down and bottom-up IEC 61850 engineering
- What substation commissioning includes
- Commissioning dossier: test records, reports and as-built
- Redundant gateway and dual link to the control center
- PRP and HSR (IEC 62439-3): redundancy with zero recovery time
References
- CIGRE, Technical Brochure 329, Guidelines for specification and evaluation of substation automation systems, WG B5.18, 2007.
- CIGRE, Technical Brochure 637, Acceptance, commissioning and field testing techniques for protection and automation systems, 2015.
- IEC 61850-3, -4, -6 and -10.
- IEC 62443, security for industrial automation and control systems.
- IEC 62351, communication security for power systems.
- IEEE 1613, environmental and testing requirements for communications networking devices in electric power substations.
Frequently asked questions
Should the specification name relay brands?
In general it is better not to: functions, standards and performance requirements are specified. There are reasonable exceptions, such as requiring compatibility with the brand already installed in an extension or with the utility's standard, and in that case the tender justifies it.
Which standard governs a SAS specification?
There is no single standard. IEC 61850 covers communication and its Part 4 project management; CIGRE published a guide for specifying and evaluating a SAS (TB 329); and each utility usually has its own technical specification, which prevails where it applies.
Which files must be delivered at the end of the project?
At a minimum, the final SCD and the files of each IED, the settings and logic of relays and controllers, the gateway and HMI configuration, the network configuration, the final signal list and the approved test records. All in versions consistent with what is installed.