IEC 61850 standard-based goose message application for a shunt capacitor bank protection

Abstract

Capacitor banks play an important function in power systems, helping to enhance voltage profiles, reduce power system losses, correct power factor, and release system capacity. It is consequently critical that they are successfully and efficiently safeguarded through the use of quick and dependable protection solutions. When capacitor banks fail, they cause maintenance concerns, making it difficult to identify broken units/elements and time consuming for specialists, perhaps resulting in voltage control issues or the loss of any of the above-mentioned benefits. As a result, the goal of the research is to use the dedicated voltage differential protection function to identify the unit or element failure within the capacitor bank. The failure of capacitor elements either above or below the tap results in differential voltages detected and these differential voltages are calculated for each element failure to determine protection settings for alarm and trip conditions. To determine the fault location either above or below the tap, the sign of the detected differential voltages is used, with a positive sign indicating the fault is below the tap while a negative sign indicates the fault above the tap. These voltages are monitored per phase and this minimizes fault-finding times as the fault location is identified during fault reporting. The voltage differential protection scheme is used as the main protection of the shunt capacitor bank for faults within the capacitor bank, while for backup protection against external faults, overcurrent and over/under voltage protection schemes are used. A simulation of the network on DIGSILENT software package is performed in order to test backup protection schemes for faults outside the shunt capacitor bank installation. Two modes of operation are considered: i) Alarm, which is activated when a few capacitor bank elements fail but the bank can still be operated for a short period of time, and ii) Trip, which is activated when differential voltages detected result in the capacitor bank operating in an unsafe manner, requiring the bank to be disconnected from the power system network. The use of system-based testing for shunt capacitor bank voltage differential protection function testing is explored. A lab-scale test bench is setup to test the implementation of shunt capacitor bank protection for both main and backup protections. The protection settings calculated are applied to a SEL 487V protection relay and the network under study is simulated in the RelaySimTest software package for system-based testing functionality which does not only test steady state conditions but transient state conditions also. A local area network is setup which consists of the SEL 487V protection relay, SEL 3555 RTAC, SIEMENS RUGGEDCOM RSG2288 network switch, SEL 2488 GPS clock, OMICRON CMC 256 plus and CMC 356 units, and RelaySimTest software. To test the voltage differential function, two Calibration and Measurement Capability (CMCs) test injection devices, representing bus bar and capacitor bank tap voltages, are employed to link the VZ and VY channels of the SEL487V protection relay. Using GPS signals from SEL satellite clock SEL 2488, the two CMCs are synced in the RelaySimTest program. RelaySimTest simulates capacitor element failures scenario by closing the circuit breaker across the bank element/s, causing an impedance shift and thus influencing voltage. For a shunt capacitor bank with three logical nodes defined, i) A87PDIF1 (alarm mode) and ii) T87PDIF1 (trip mode), iii) H87PDIF1 (high set), the IEC 61850 GOOSE messaging application is explored. The A87PDIF1 Logical Node is further divided into two Logical Nodes for fault location identification, i) AA87PDIF1 for faults above the tap and ii) BA87PDIF1 for faults below the tap and these are monitored per phase. The lab-scale simulation results are analysed and proved that the protection schemes implemented using the system-based testing methods prove to be very useful for testing steady state and transient conditions. The system-based testing of the protection scheme and its simulation results are close as possible to real life conditions at site. IED Scout is used to analyse the IEC 61850 GOOSE simulation results. For SCADA HMI applications, Manufacturing Message Specification (MMS) is also utilized to collect data from the protection relay utilizing Buffered Report Control Block (BRCB) and Unbuffered Report Control Block (URCB) subscribed by the substation gateway SEL 3555 RTAC device. SEL AcSELerator Diagram Builder software is used to develop the HMI which is loaded into the RTAC device for online viewing of alarms, events and measurements. The research provides insight into shunt capacitor bank protection and the implementation of the IEC 61850 standard. The project outcomes assist industry specialists to better understand and implement voltage differential protection schemes for shunt capacitor banks while also introducing system-based testing methods to the industry, which provide advantages over conventional testing methods.