With the development of power technology, the construction of smart substations is booming. The types and quantities of secondary equipment in substations have increased simultaneously, and the detection technologies and standards for secondary devices have become increasingly improved. Commissioning before putting secondary equipment into operation, as well as verification and maintenance after commissioning, have become key daily operation and maintenance work for smart substations. Herein, we briefly introduce the main testing items for secondary equipment of smart substations and the required testing instruments.

The secondary devices of smart substations mainly include: protection devices, measurement and control devices, merging units, intelligent terminals, instrument devices, switches, network analyzers, etc.

1. Merging Unit

The merging unit is the secondary-side hub of a smart substation. It receives and merges the analog signals (mainly voltage and current) of the local bay sampled from transformers, performs A/D conversion into optical digital signals, and transmits them to the corresponding secondary-side devices, including protection devices, measurement and control devices, fault recorders, network analyzers, instruments and so on.

The main items for on-site verification are ratio error, phase error, time delay and first cycle. The Relaystar-7000 Integrated Digital Relay Protection Test System and Relaystar DCU-500 Merging Unit Test System can meet the requirements of on-site testing items.

△ Relaystar-7000 Integrated Digital Relay Protection Test System

△ Relaystar DCU-500 Merging Unit Test System

In addition to on-site verification items, research institutions and secondary device manufacturers also need to conduct tests such as time synchronization, time keeping, synchronization, frame loss, jitter and dual AD difference. The Relaystar DCU-500 Merging Unit Test System can meet the above testing requirements.

2. Intelligent Terminal

The intelligent terminal can realize A/D and D/A conversion of switch quantity signals, blocking signals, etc. between protection devices (measurement and control devices, merging units), circuit breakers and networking systems. It receives GOOSE tripping commands issued by protection devices, controls the tripping or reclosing of circuit breakers through electrical signals, and receives state change signals of circuit breakers, converts them into optical signals and uploads them to the network.

The main items for on-site inspection are uplink time and downlink time. The Relaystar-6000 Optical Digital Relay Protection Tester, Relaystar-7000 Integrated Digital Relay Protection Test System and Relaystar DCU-500 Merging Unit Test System can all meet the testing requirements.

For research institutions and secondary device manufacturers that need to conduct tests under extreme working conditions and abnormal working conditions, the Relaystar-7000 Integrated Digital Relay Protection Test System is recommended.

3. Protection Device (Measurement and Control Device)

The sampling mode and network protocol of protection devices in smart substations are different from those in conventional substations, requiring digital signal tests such as frame loss, misorder, jump, dual AD difference, wrong value, overflow and heartbeat message. Protection devices adopt SMV sampling and GOOSE tripping mode, which can be tested by the Relaystar-6000 Optical Digital Relay Protection Tester and Relaystar-7000 Integrated Digital Relay Protection Test System. For protection devices adopting conventional sampling and GOOSE tripping mode, the Relaystar-7000 Integrated Digital Relay Protection Test System can be used for commissioning.

4. Instrument Device

Instrument devices in smart substations receive optical digital signals, with the main testing items being SMV signal acquisition and precision verification. The Relaystar-6000 Optical Digital Relay Protection Tester, Relaystar-7000 Integrated Digital Relay Protection Test System and NSA-60 Handheld Optical Digital Signal Analyzer can meet the testing requirements.

△ NSA-60 Handheld Optical Digital Signal Analyzer

5. Network Equipment (Switches, Network Analyzers, etc.)

The main testing items include network congestion, redundancy, frame loss, network traffic, network storm and operating condition. The NSA-60 Optical Digital Universal Test and Analysis Instrument is recommended.

△ NSA-60 Optical Digital Universal Test and Analysis Instrument

6. Online Monitoring of Secondary System in Smart Substations

It is mainly used for real-time online monitoring, online operation and maintenance, analysis, diagnosis and prediction of smart substations. The BDZ-101 Relay Protection Condition Monitoring and Analysis & Diagnosis System for Smart Substations is recommended for comprehensive monitoring and intelligent diagnosis.

△ BDZ-101 Relay Protection Condition Monitoring and Analysis & Diagnosis System for Smart Substations

7. Transformer Hexagonal Diagram

The high, medium and low sides of transformers in smart substations are located at different positions: the high-voltage side is generally on-site, and the low-voltage side is generally in the low-voltage room, with a long distance between them. The YD-300B Wireless Telemetry Voltmeter-Ammeter Phase Meter can conveniently and quickly complete the measurement of voltage, current, phase, etc. at multiple remote locations.

△ YD-300B Wireless Telemetry Voltmeter-Ammeter Phase Meter