Controlling participating generators to be able to close a non-generator circuit breaker isn’t an easy task. Or, wasn’t in the past. Now ABB has something new to offer. My guess is that power system integrators will love this innovative, simple and cost-efficient solution.
Let’s start with the question: Have you ever thought about using a protection relay for generator auto-synchronization?
At first this might sound a bit far-fetched, but think about it for a moment. A protection relay that is in charge of a generator’s electrical protection has already most of the primary system interface required by an auto-synchronizer. The protection relay controls the generator circuit breaker trip circuits. It further measures the voltages across the circuit breaker, or at least from the generator side. The protection relay monitors the positions of the primary switching devices and displays them on a local human-machine interface (LHMI). So what’s required on top of the existing interfaces? Well, the possibility to control prime mover speed, the generator’s excitation, the closing of the generator circuit breaker and, of course, the actual auto-synchronizer functionality within the protection relay.
What do we gain from this approach?
Firstly, availability: we’ll have a synchronizer for each generator, not just one synchronizer for all generators. Secondly, we gain smoother controls during synchronizing process, since the synchronizer setting parameters can be optimized by taking into account each generators individual behavior/characteristics. Thirdly, simpler local operations: each protection relay LHMI would contain full support for local manual or automatic synchronization controls. Fourthly, reliability: the hardened protection relay platform offers by nature a robust foundation for auto-synchronizer. And finally, we also reduce engineering time: standardized solution as a part of the protection relay configuration saves time.
Requirement to be able to close a non-generator circuit breaker in a synchronized manner leads to complicated solution – right?
Yep, depending on how complex primary network topology is, this requirement can lead to complicated error borne designs. Switching status of the network primary components and availability of the generators within the system has to be constantly monitored. The available generators have to be engaged according to which circuit breaker within the system is to be closed. Typically the design includes an auto-synchronizer installed into a synchronizer panel, which also contains all necessary meters, control switches, position indications, etc. for local controls. This panel further contains the “brains” of the system in a form of complicated auxiliary relay based logic, or as a modern alternative, a programmable logic controller (PLC).
Can we do it better, simpler and in a more cost effective way?
Yes we can. Let the protection relays take over the complete system. The protection relays communicate with each other using binary and analogue GOOSE signaling as per IEC 61850-8-1. They share information on primary network switching status, availability of generators, plus voltage and frequency deviations across the circuit breaker, which is under synchronization. The protection relays’ LHMIs cater for the situational awareness and the local controls. Once again, each circuit breaker has its’ own auto-synchronizer function as a part of the protection relay’s functionality.
Can such a communication-based system be reliable?
Yes it can. We use redundant communication topologies like PRP or HSR. The GOOSE signaling is constantly supervised and as a result of this, early warnings are issued. The actual auto-synchronizer functions are distributed into the protection relays within the system. A single protection relay fault has only a limited impact for the complete system.
Want to learn more?
Please take a look at our conference paper Plant-wide autosynchronization, Based on IEC 61850 and protection relays presented in PCIC Europe 2018 and written by Dibyendu Bhattacharya and Alok Gupta from BP, Arinjai Gupta and myself from ABB.
Automatic synchronization is one of the application packages you can choose with your new REX640 relay, the king of ABB’s Relion® protection and control family of relays. REX640 will be released for sale during quarter four, 2018.
About the author
Olli Rintamäki works as a product line manager at ABB Distribution Solutions in Vaasa, Finland. He has authored or co-authored a number of conference papers.
