Automated fault analysis and relay protection performance evaluation
Журнал «Цифровая подстанция (Digital Substation)»
This article represents results of design for information-analytical system for automatic analysis of fault events and protection performance evaluation (hereinafter – the System) applicable for deployment to substations and power plants. The main objectives of the development of the System were the following:
creation of common information model of a substation or power plant that contains topology and characteristics of the primary equipment, connectivity schemas of current and voltage transformers and associated protection devices, settings and configurations of relays, semantics of their signals and recordings;
organization of fault data collection and preprocessing available for further automatic analysis;
automatic execution of fault event identification and fault location;
automatic express fault analysis based on available preprocessed data at substation/power plant level;
automatic analysis and evaluation of starting and tripping of relay devices during fault events.
2. Data integration
As a format for recording non-operational data, proprietary formats of manufacturers of DPR devices and stand-alone DFR are often used. There is a possibility of processing waveforms records using third-party software after you export data from native format to COMTRADE text format (IEC 60255-24). When you export data from native format to COMTRADE format, usually, DFR and DPR device manufacturers use just two types of files out of a possible four, namely: "Configuration file" with the extension ".CFG" and the "Data file" with the extension ".DAT". In this case, the additional "service" information contained in the manufacturer's source file, for example, information about the device itself, its configuration, settings and relay starting conditions, is not exported, as well as the type and location of the short-circuit in the case of the presence of a fault location function.
To solve the problem of joint analysis of fault event waveforms received from IEDs and DFR devices of various manufacturers, it is necessary to ensure the implementation of uniform requirements for the formation of COMTRADE files on the basis of the internal data format of manufacturers, in particular, the requirements for the mandatory use of the following file types: «Header file» with the extension ".HDR" and the "Information file" with the extension ".INF".
During the development of the System, the collection of operational and non-operational data into a single database of the power object server was carried out using standard information exchange protocols: IEC 61850, IEC 60870-5-104 for operational data; IEC 61850, IEC 60870-5-103 for non-operational data. Data integration was accomplished through the use of common information model (IEC 61970/61968), which was expanded with additional semantics to describe DPR and DFR devices and identification of signals recorded in COMTRADE format.
3. Information base for modelling functions
Tools for editing and updating the design model of the electrical network were implemented in the System by supporting the import of CIM XML files formed on the basis of the IEC 61970/61968 group of standards. Network topology state in the pre-fault time is determined by the actual data of circuit breakers statuses for the specified time (near the time of the analyzed fault event) received from the SCADA of the power system by transmitting the CIM XML file with the current topology of the design model of the electric network for the specified times.
Another issue solved is sufficient detailing and verification of relay models used in modeling their operation under various disturbances: it is required to achieve correct operation of protection devices models in the power system model for all types of fault disturbances. To accurately imitate the operation of the relay protection devices, the corresponding relay protection devices models contain identical composition and characteristics of measuring, starting, executive or blocking elements (current cutoff, overcurrent, distance, power direction relay, etc.), as well as the basic logic (taking into account the program overlays) reproduced from the available manufactures documentation.
4. Algorithmic support for analytical functions
Evaluation of protection operation in the system results in the corresponding criteria that are automatically recommended for the user:
Incorrect operation: Unnecessary; False; Failure; Admitted.
The task of evaluating correct relay operation using models is solved by the following groups of functions:
Creation of the power system simulation model, including topology model, characteristics of primary and secondary equipment, sufficient to perform transients calculations with variety types of fault conditions.
Estimation of the topological state of the primary equipment in the power system based on status data of switching devices in the pre-fault condition.
Receiving the results of fault location functions and reproducing these fault events on power system calculation model.
Transient calculation in the power system, taking into account all types of unbalanced conditions, all types of fault events and locations, which can be identified by the fault location function;
Adjustment (if necessary) of primary equipment models parameters based on actual fault data with defined fault locations to ensure that the results of the modeling comply with actual collected and processed field data.
The actual replica of relay configurations and their functional logic settings in their digital twins used in the modeling of power system transients specially in short circuit calculations.
Calculation of output analog and discrete signals from relay models for each protection functions based on the analysis of input signals connected to primary power system equipment models, and modeling of the internal functional logic of relay protection.
Building reference event-tree logic for relay starting and tripping conditions for a particular fault event data in the power system model - formulating requirements to protection expected operation.
Comparison of output signals of relay models with actual signals collected and processed from substation level, deviation control and alarming.
Determination of performance indicators of relay operation for each protection function based on the power system modelling.
The use of relay models provides the ability in the System to compare field measurements for fault events with actual protection settings that determine operation of the device.
Concept idea of System is represented in fig.1.
Fig.1 Concept idea
The article presents the results of work on the design and implementation of the industrial prototype of information-analytical system for automatic fault analysis and protection performance evaluation. Information model and algorithmic services of the System were developed according to IEC 61850, IEC 61970/61968 specifications and recommendations, however the information metamodel was extended with new semantics. Performance evaluation and detection of possible relay failures is based on automatic comparison of information received from DPR, DFR, RTU field-devices with the expected etalon operation of relay protection obtained through digital modelling.
The technical solutions presented in the article differ from all existing at the moment realizations in the following features:
the use of information model to represent the initial data of the analysis in a unified, machine-understandable format: electrical topology information, characteristics of the power equipment, setting parameters and algorithms of relay protection devices operation, the semantics of operational and non-operational data;
- the use of detailed calculation models of power system and relay protection devices to perform relay protection performance evaluation according to the conditions of starting and tripping during fault events.
 International Council on Large Electric Systems. New Trends for Automated Fault and Disturbance Analysis. CIGRE WG B5.20 Report 2012.