What to Do When the Analog Output Channels of a Relay Protection Tester Are Insufficient?
Many test engineers encounter the problem of insufficient analog output channels in relay protection testers during their work. For example, when testing transformer differential protection, if it is necessary to simulate the situation where all sides of a three-winding transformer have current input; for bus differential protection, multiple bays need to input current simultaneously; and there are also some applications related to system control, such as load transfer devices, which require simultaneous connection of three-phase current and single-phase voltage for each bay, as well as three-phase voltage for each bus. As a result, a single tester may be stretched thin. What to do when the analog output channels of a relay protection tester are insufficient? Below are several methods to expand the analog output channels of a relay protection tester:
1. Use an amplifier
The amplifier also has 4 voltage and 6 current channels, and the voltage and current parameters are exactly the same as those of the CMC356. In addition, C can also cascade more amplifiers to make the application more flexible.
2. Two relay protection testers output synchronously, with the 4th voltage channel as the synchronization control
The 10th switch input channel of the relay protection tester can input a synchronization signal of 15-70Hz, so that its own analog output keeps pace with the synchronization signal. The 4th voltage channel of the first relay protection tester serves as the synchronization signal. In this way, two relay protection testers can provide 7 voltage and 12 current channels. It should be noted that this method can only be used in the QuickCMC manual test module and the state sequence module.
3. Multiple relay protection testers use clock synchronization signals for synchronized output
Relay protection testers have clock synchronization methods such as GPS/IRIG-B/PPS second pulse/PTP1588, so multiple relay protection testers can be synchronized to output at the same time, thereby meeting the needs of multiple analog channels. Of course, this method is mainly suitable for manual test modules and state sequences, etc.
4. Use RelaySimTest software to control multiple relay protection testers for synchronized output
RelaySimTest (RST) is software that uses real-time simulation for system testing. After designing the system topology in the software and setting various faults and control sequences, multiple relay protection testers are used to simulate the voltage and current output of each node of the system to the device under test (such as relay protection or stability control devices). Therefore, RST naturally requires the same software to control multiple testers.
RST uses IRIG-B or PTP1588 clock synchronization signals to synchronize each relay protection tester, and the number of relay protection testers that can be synchronized and controlled is theoretically unlimited. The interface of RST is very simple, and it can also be used when only multiple relay protection testers need to output synchronously without simulating complex power systems.
