MTEP activity

Purpose and principle of operation :

Device is intended for fast identification of earthfault feeder and information transmission to upper SCADA system. It is adapted for operation in electrical network with isolated or compensated neutral. Principle of operation of device is based on methods of digital analysis of initial electromagnetic processes in electrical network using digital filters. Device detects earthfault by comparing measured and calculated values of voltage and current of initial process. Neither parameters of earthfault place nor parameters of specific electrical grid have influence to the reliability of detection of earthfault feeder. Device also records short term, self extinct earthfaults in the feeder. Device does not need structure of the lines it is connected to, diagram of all the lines connected to the busbar and information about spread of wires in the OHL support. It is extremely useful for      industrial plants which service HV cable lines with high power motors and generators connected to it.

Technical characteristics :

• smart algorithm of analysis of fast transients for location of earthfault feeder based on recording of variable step transient processes;
• recording and analysis algorithm of short term and long term earthfaults;
• automatic notification of dispatcher of electrical grid about long term earthfaults in the feeder (if needed also about short term self extinct earthfaults);
• information transmission protocols : IEC 60870-5-103 or IEC 61850;
• duration of recorded process for identification of earthfault feeder ≤ 100 µs.

Technical parameters :  

Measurement ranges :

• Zero sequence current   0,05 – 100 A
• Zero sequence voltage 5 – 250 V
• Duration of recorded process of current and voltage 5 – 100 µs
• Measurement frequencies up to 10 MHz

Application :                    

Distribution electrical network (utilities and industry) with isolated or compensated neutral.

Advantages :

• reduced expenses of fault place identification by electrical network operator;
• reduced number of disconnections of electrical grid (when earthfault turns to short circuit);
• higher reliability of electricity supply;
• reduced probability of accidents in electrical grid segment;
• few times smaller investments into network renovation as well as repairing of network and electrical equipment;
• safer, more stable and less loss-making production process in industry.

Connection :                    

Device is connected to cable current transformer of the feeder and open delta circuit of voltage transformer.

Purpose and principle of operation :

Device is intended for recording of fast transient processes (atmospheric (lightning) overvoltages). Device records amplitude, its duration and time of origin  of voltage increase above maximum permissible operation voltage of electrical network. Device performs actual automatic calculation of insulation reserve of electrical network equipment (residual withstand) using recording of fast transient processes and building integral characteristics of overvoltages according to the character of recorded transient processes and utilizing evaluation algorithm of the influence of qualitative parameters of records to the status of electrical network (insulation reserve). Implemented evaluation algorithm of insulation reserve compares total integral characteristics of overvoltages and maintenance time of equipment with insulation test (limit) voltages of equipment.

Technical characteristics :

• Supervision of integral overvoltage characteristics (insulation reserve) according to the character of recorded transient processes;
• Sampling step 50-100 ns;
• Number of recorded transient processes – 50;
• Number of analyzed transient processes – unlimited;
• „on-line“ integral evaluation of insulation reserve caused by influence of overvoltages;
• Transmission of information – Ethernet;
• Smart algorithm for actual supervision of insulation reserve of electrical network equipment.

Measurement range :

• Phase voltages  0 – 250 V
• Phase currents (can be measured)  0,05 – 100 A
• Zero sequence voltage 5 – 300 V
• Measurement frequencies up to 10 MHz
• Measurement duration for analysis of single record up to 500 ms

Application :  

Device is very useful for electrical utilities and industry since enables more precise forecast and planning of repairing and preventive maintenance works as well as  optimally allocate financing to perform these works. It is very relevant to use the  device in industry for supervision of insulation of electric motors and generators since insulation of this equipment ages 2 times faster than other electrical  equipment. Overvoltage recorder constantly supervises quality of protection of electrical network by surge arresters (their protective characterics deteriorate with     time) and respectively helps to ensure safety of electrical network.

Based on device records of overvoltages in 6-10 kV cable network with isolated  neutral and duration histograms it is possible to determine the level and duration of overvoltages affecting insulation and forecast preventive tests of the cables.

Advantages :

• reliable recording of overvoltages;
• supervision of change of reserve of residual withstand of insulation of electrical network equipment;
• forecast and planning of repairs or need of preventive maintenance.

Connection : 

Device is connected to phase outputs and circuit of open delta of voltage transformer.