Author: Y. Korniyenko, head of advanced development sector of traction substations department, PrJSC PLUTON
International Technical & Economic magazine "Ukrainian railway". – 2016. - № 10 (40). – P. 14-19
Innovative solutions for traction substations relay protection
PLUTON has many years' experience in development and application of automatics and relay protection devices for DC traction substations.
Recently, in connection with increased traffic flow and reduced rolling stock traffic interval grows a demand for intelligent relay protection devices, provided for contact networks protection against overloads and short circuit currents. Firstly, this is because of that fact that during emergency events that occur in traction power supply networks after actuation of high-speed circuit breaker, fast and accurate estimation of emergency mode for the most effective decision-making and recovery of electric power supply of power system and rolling stock in the shortest possible time is critical factor for operational personnel.
For electric power systems of traction power supply that have transience properties of transient processes, estimation of relay protection events and circuit breakers should be carried out with application if intelligent microprocessor devices. Data about circuit breaker operation, as well as current and voltage parameters in contact network before emergency process are critical during evaluation. Data about operation of control systems logical section, as well as sequence of events before and during emergency mode in power supply of traction rolling stock are of particular importance for decision-making.
All of that requires application in DC switchgears of intelligent relay protection microprocessor units with appropriate functions and characteristics, such as: collection of emergency processes data, providing operational personnel with these data in minimum time period for further analysis, monitoring of traction power supply parameters in real time mode for prevention of emergency processes occurrence etc. PLUTON strives to make a contribution to development of electrical engineering around the world and uses innovations and achievements for continuous improvement of products and solutions. One of such products is innovative SMTN-3 traction network monitoring and protection system that represents the third generation of protective devices based on advanced technologies.
SMTN-3: general information
SMTN-3 traction network monitoring and protection system is provided for:
- traction network protection against short circuit current and harmful overloads;
- traction network parameters monitoring;
- data acquisition for the following analysis of emergency processes.
SMTN-3 are used in switchgears for traction substations of city transport, metro, electrified railways, industrial enterprises, as well as mining enterprises.
The system is a combined microprocessor relay protection device. Application of modular microprocessor architecture, in combination with modern surface-mount technologies, provides high reliability, high computing capacity and high-speed operation, as well as sufficient measuring accuracy of electrical values and time intervals that gives possibility to increase protective functions response.
Algorithms of protection and automatics functions, as well as device connection diagrams, implemented in the device, are developed in cooperation with power networks representatives that simplifies implementation of new techniques for designers and operational personnel. Components base of input and output circuits provides compatibility of SMTN-3 with any types of automatics devices of various manufacturers — electromechanical, electronic, analog-to-digital, microprocessor. SMTN-3 can be supplied individually for application at operating facilities during their modernization or reconstruction. Besides, SMTN-3 can be supplied as a part of switchgears during capital construction of electrical power facilities, as well as in assembly with remote measurement systems cabinets, ACS, data management and control systems etc.
SMTN-3 can be incorporated into ACS and data management and control systems as a low-level subsystem and can fulfill telecontrol and remote signaling functions.
SMTN-3 provides the following operational capabilities:
- measuring of current and voltage waveform and value in traction network in various modes, including upon short circuit in line;
- protection of traction network against short circuit currents, including low currents of remote short circuits and overloads;
- oscilloscope recording of current and voltage waveform and value upon short circuits into non-volatile memory (detection of one of emergency process protections in traction substation);
- storage and displaying oscilloscope records, as well as data transfer into low level system (or into PC) for further analysis;
- internal configuration setting (protection setting input, selection of protective characteristics, number of protective degrees etc.) using software;
- local and remote input, storage and displaying of protection settings;
- storage of two sets of settings and switching of sets of settings in response to external signal;
- storage and output of data about number and time of protection tripping;
- analysis of currents distribution between cathodic switchgears.
System structure
SMTN-3 system is constructed on the basis of modular concept. Thereby, SMTN-3 consists of several standard parts. Some modules are obligatory; application of other modules is optional and depends on Customer’s requirements to the system. Modular concept provides independent operation of failure-free modules in case of failures or troubles in adjacent modules.
SMTN-3 system structurally and functionally consists of next obligatory units:
- measuring module is located in power circuit zone (busbar compartment);
- converting module is located in low voltage zone (control section).
Measuring and converting module are connected to each other with optic fiber cable that provides data transfer between modules, as well as galvanic isolation between high-voltage measuring and secondary circuits.
Measuring module
Main functions of measuring module:
- coordination with primary sensors (shunts, voltage dividers);
- galvanic isolation of low voltage circuits against high traction network potential, using galvanic isolated power supply unit;
- conversion of analog input electrical values for their coordination with converting module interfaces;
- pre-filtration of input signal on the basis of analog and digital filters;
- transfer of converted analog input electrical values into converting module using optic fiber cable.
Converting module
Converting module carries out processing of all data received from measuring module and other additional modules, as well as from discrete inputs. Module consists of several computing systems connected to each other with data busbars.
Main functions of converting module:
- primary processing and accumulation of actual information received from measuring module;
- normalization of current and voltage values;
- diagnostics and monitoring of data received from measuring module for reliability;
- protection functions (analysis of measuring module data according to protection algorithms);
- forming of signals for emergency tripping of switching devices according to protection functions;
- logging and storage of data related to traction network emergency processes;
- system events logging;
- storage of system settings;
- system self-diagnostics;
- connection with ACS TP low level system;
- access to change and setting of system parameters using HMI interface.
Optionally, the system is equipped with the following systems (modules) that extend functional range of the system as a whole:
- line tester (short circuits tester);
- cable insulation control system.
Line tester (short circuits tester) allows determining line impedance before high-speed circuit breaker closing. In case if line impedance is lower than the setting parameter, the system issues a prohibition to close high-speed circuit breaker.
Cable insulation control system continuously monitors cable insulation resistance and gives a warning signal in case of insulation degradation. A signal to open high-speed circuit breaker is given in case of cable insulation failure.
SMTN-3 protective functions
SMTN-3 provides failure-free reliable system operation and filtration against false tripping. It carries out the following functions (see Table 1)
Table 1 False tripping protection functions
| Name of protective functions | Value | Code ANSI | Application |
| Instantaneous overcurrent | І0 | 50 | Near short circuit protection |
| Overcurrent protection | Іmax | 76 | - |
| Current rate of rise protection |
di/dt | - | Near short circuit protection |
| Current increment directional protection |
ΔI | - | Near short circuit protection |
| Overvoltage protection | Umax | 59 | Overvoltage protection |
| Undervoltage protection | Umin | 27 | Undervoltage protection |
| Thermal protection | I(t) | 49 | Protection against remote short circuit (thermal protection) |
| Breaker failure | Circuit breaker failure protection | BF | - |
Nowadays, on the territory of CIS countries are mainly applied relay protections with slow and outmoded RS-485 communication interface that does not allow to operating personnel receiving data about emergency processes within a short period. Implementation of data transfer technology based on Ethernet into SMTN-3 is the first key step in substation automation and qualitative improvement of speed of data acquisition from the device. With integration of this technology into automation systems, PLUTON incorporated more than 10 years’ experience in production of measuring and protective devices with modern communication technologies. Effective connection of relay protection devices to field proven remote control complexes and data acquisition systems, as well as to local networks is possible from now for joint application of accumulated data and further analysis, taking correct decisions within a short time or in in a real-time mode. Therewith, reliability and operational performance of new and modernized substation increases.
Ethernet as an important step in protective devices evolution
Events and parameters logging
SMTN-3 generates and stores the following records:
- events log;
- failures log;
- emergency oscilloscope records.
Records are stored on nonvolatile solid data storage medium that guarantees data storage in case of devices power supply interruption, and high reliability.
SMTN-3 system provides generation and storage of emergency oscilloscope records. Emergency oscilloscope record generation is performed when one of protective functions operates. SMTN-3 keeps in memory up to 200 emergency events logs. Upon exceeding the limit, new log will be saved instead of the oldest log.
Emergency records can be viewed using WEB interface, read by upper level system via Ethernet interface or saved on external USB disk for later analysis using a PC. SMTN-3 system also records maximum current and voltage values. Upon exceeding new measured current and voltage values, logged before, new values are recorded instead of the old ones. A comparison is carried out independently for current and voltage channels. Recorded maximum values can be reset to zero, whereby cycle of new maximum values registration will start anew.
Human-machine interface (HMI)
SMTN-3 system involves the following methods of parameter setting both the system, and protective functions parameters:
- local interface «Human-Machine» based on LCD touch panel;
- remote «Human-Machine» interface based on WEB technologies;
- remote access to the unit using ModBus TCP/IP protocol, for upper level systems, power supply control systems etc.
Remote «Human-Machine» interface based on WEB technologies is an integrated WEB server in each SMTN-3 converting module. It does not require additional software installation on PC. This interface is used for data configuration, display and analysis, collected by SMTN-3 system. Connection with SMTN-3 WEB server can be carried out through Ethernet cable or via PC, tablet computer or smartphone connection. For operation of SMTN-3 WEB server is required only installed WEB browser on the device and corresponding access to local network. «Human-Machine» interface can be executed in English. Interface can be executed in other languages.
Reliability
All protective and control and measuring equipment, including SMTN-3, produced by PLUTON, undergoes careful tests in own certified testing laboratory.
Special attention during tests is paid to checking of system behavior upon simulation of various failures. Upon various certainly false signals, the system operates sustainably, according to the specified characteristics. Such false signals, if they happened in reality, would cause emergency power supply network tripping.
System design concept with application of interference-free data encoding principles and other know-hows led to development of a device that operates upon constant process of system self-diagnostics, its parts and modules. Continuous monitoring by SMTN-3 system of components and data transfer channels with self-diagnostics function significantly reduces necessity in periodic maintenance and simplifies maintenance process carried out by substation personnel. According to reliability calculations, mean time between failures (MTBF) of SMTN-3 electronics is about 20 years. That all shows extremely high reliability and system performance even upon severe operational conditions.
Certificates and compliance with the requirements of international and European IEC standards
PLUTON offers only trusted products of high quality at the market. Therefore, SMTN-3 system passes certified tests for compliance with the requirements of international and European standards at foreign testing laboratories.
For instance, in foreign testing laboratories SMTN-3 system passes the following tests:
- tests for compliance with the requirements to electromagnetic compatibility;
- mechanical tests;
- climatic tests.
Special attention during SMTN-3 development was paid to compliance with the requirements of international and European standards related to electromagnetic compatibility, i.e. the device operates in conditions of traction substations (industrial conditions) at high level of electromagnetic interference. Operational stability and no false, incorrect SMTN-3 system actions in such severe, from the perspective of electromagnetic interference, conditions has meaning of high priority for reliability of switchgears and traction substations in total.
Application for modernization
Very potentially promising direction is application of SMTN-3 as a relay protection device during substations modernization. It is based on that fact that SMTN-3 is an all-sufficient device that does not require another additional control equipment and/or additional communication systems with telecontrol complexes. Due to input/output discrete signal ports, SMTN-3 can be easily integrated into existing control circuit of switchgear.
Looking into the future
PLUTON main goal is to remain a leading company in production of high-quality equipment and always offer to its Customers the best service and products of the most modern level that meet international standards and innovative technologies, as well as provide safety and comfort of people.
PLUTON does not fix on achieved success, and constantly monitors market needs, explores global trends, tends to stay informed about the latest achievements of science and engineering in the field of electrical engineering. PLUTON plans call for implementation of hi-tech intelligent developments around the world and further promotion of the latest innovative ideas in the field of power distribution, relay protection and automatics on the market.