Software Based Centralized Protection: commissioning experience

Authors: Alexey Anoshin, Aleksandr Golovin, and Nikita Svistunov, TEKVEL R&D Ltd., Russia


In 2018 Tekvel signed several contracts to commission centralized protection system based on servers and independent software. In this article we would like to share our experience and discuss some of the problems, that might require special attention from utilities on the way to mass deployment of centralized PAC systems.

General Overview of ISAS Centralized PAC
There have already been introduced a number of concepts of centralized systems starting from devices capable of protecting multiple feeders, up to fully centralized systems capable of handling of the whole substation protection and automation in a single high-performance server.
Some of the introduced systems are tied to specific hardware, while others might run on independent platforms. 

In our case we have been dealing with the following architecture of the system:

  • ISAS is hardware-independent (i.e. it might be running an almost any 86_64 arch machine)
  • ISAS runs under Linux OS with special real-time kernel patches
  • ISAS allows multiple system architectures from fully decentralized (i.e. independent instances of the software running on independent servers) to fully centralized (i.e. one server is running one instance of the software implementing functions for all bays of a substation) as shown in Figure 1.
  • ISAS architecture allows redundant schemes where multiple servers back-up each other
  • The configuration of ISAS is 99 percent based on the SCD file, that fully describes the whole PAC system, including protection settings
  • Monitoring and control operations are performed via panel PC HMI(s) also fully configurable with SCL-like files and communicating to ISAS servers via MMS
  • SCADA system (if required) is connected to ISAS servers via MMS as well as HMIs

Although different architectures are supported by the software, the most common architecture we’ve seen in real applications is centralization of most functions and using back-up server for redundancy. Also due to local regulations a separate server might be required for Metering, Fault Recording, etc. (Figure 2).

We have been commissioning 3 projects with ISAS (fully or partially):

  • 110/10 kV substation fully running PAC for the whole substation in two servers with ISAS software with conventional transformer differential used as backup protection (referred as Project 1)
  • 110/35/10 kV substation with multiple ISAS servers. ISAS is used there as the only control system, while protection is fully duplicated by conventional hard-wired relays (Project 2)
  • 35 kV shunt reactor protection at 220 kV substation using ISAS (Project 3)

In terms of general approaches all of these three projects had much in common:

  • Combined SAMU+SCU devices (hereinafter referred as field devices) were installed in the switchyard or in secondary equipment compartment of the switchgear (see Figure 3).  Field devices are capable of processing binary inputs and analog current and voltage signals and publishing GOOSE and SV messages respectively for each kind of signal. They are also capable of subscribing to GOOSE messages and switching binary outputs based on the data in the GOOSE message
  • Notable that field devices used in those projects had modular design allowing same approach for different bays (i.e. different number of signal)
  • For 110 kV bays multiple (two) field devices were used per each bay to ensure reliability of the system. Both field devices were subscribing to data from both main and backup servers eliminating single point of failure
  • For 10 kV bays single field device is used.
  • Process bus network has a double-star topology with PRP redundancy protocol. For smaller projects single ethernet switch is used per each PRP LAN A/B. For larger project multiple daisy-chained switches might be used within each PRP LAN A/B
  • Time synchronization for process bus network devices is provided using PTPv2 time synch protocol with time servers integrated in Ethernet switches
  • Multiple panel PC HMIs were used in larger projects, each providing monitoring and control functions for each voltage level. Typically, 10 kV HMIs were installed near the 10 kV switchgear, while 110 kV HMIs installed in the control room
  • In our case there were no projects where ISAS system was used for metering or PQ monitoring. Although technically it was possible, it has never been implemented due to regulation issues

Each project also had some specifics introduced by huge differences in the number of bays which resulted in different computation power required. In Project 1 and Project 3 there were only 2 servers (main and back-up) running ISAS software. While in Project 2 there were 6 servers: 4 running protection functions and 2 running automation and control functions (see Figure 4).
There were also differences in hardware used: in Project 1 and 3 HPE Proliant servers were running ISAS software, while in Project 2 ISAS software was deployed on DELL servers. There were also differences in network interface adapters (NIC) installed in servers (that turned out to be important.)

Power. Flexible. Easergy.
BeijingSifang June 2016