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Relay Protection


Development of Micro-Processor Equipment for Relay Protection and Automation of Power System Networks

Tech Area / Field

  • MAN-MCH/Machinery and Tools/Manufacturing Technology
  • NNE-EPP/Electric Power Production/Non-Nuclear Energy

3 Approved without Funding

Registration date

Leading Institute
NIIIT (Pulse Techniques), Russia, Moscow

Supporting institutes

  • The South-Russia State Technical University (Novocherkassk Polytechnical Institute), Russia, Rostov reg., Novocherkassk


  • Weinzetl & Hinssen GmbH, Germany, Rosrath\nPMD Scientific Inc., USA, CT, Bloomfield\nRheinische Fachhochschule Koln, Germany, Köln

Project summary

The asynchronous electric motors with capacity of 4 МW and more of normal operation of nuclear power station auxiliaries are responsible elements providing safe operation of nuclear power equipment. This fact determines the high level of requirements to relay protection devices of the specified electric motors.

The existing devices of relay protection realize the concept of maintenance of damaged electric motor disconnection from the subtransmission network. This concept was based on the opinion that expenses on damaged electric motor repairing are lower than expenses on equipment of electric motors with sensitive and high-speed relay protection devices. It is obvious that another concept of protection should be realized in relay protection of the specified electric motors development. It is to prevent the damage at dangerous abnormal modes and to distinguish damages at early stage of their development. Thus, the developed device in its essence is protective-diagnostic.

In comparison with known microprocessor devices the following new functions are provided:

– recognition during time not exceeding 10-20 % from normal start-up duration, at dangerous abnormal starting modes such as start-up with a blocked rotor (non-completed start-up), delayed start-up, rotating rotor jam. Due to this function the thermal damages of stator windings and rotor overheating will be excluded;

– recognition of short circuit modes at turn-to-turn short circuits of the stator winding (up to 1-3 % of coils in a phase), stator phase breakage and winding cores of squirrel-cage rotor breakage, supply voltage asymmetry. Due to this function the amount of electric motor damages will be reduced at turn-to-turn short circuits (at the expense of stator steel damage exclusion under electric arc influence);

– recognition of mechanical damages of the electric motor mechanism unit such as damage of bearings, skew of electric motor shaft axes and mechanism, rotor beat in stator bore. In essence the given function is diagnostic and will allow the personnel to remove the faulty unit for repairing in time.

The device technical means and software provide the following set of electric motor protections:

– differential protection in three-phase performance without time delay;

– current directed protection of zero sequence form short circuits on ground without time delay with an opportunity of turning into current non-directed protection. The protection acts as disconnection or signal;

– protection from asymmetrical modes and turn-to-turn short circuits with integral-dependent time delay;

– protection from abnormal starting modes and rotating rotor jam;

– protection from symmetric overloads with integral-dependent time delay;

– reservation of switch failure with time delay adjustable within the limits of 0.2-0.5 seconds;

– protection from voltage reduction with time delay adjustable within the limits of 0.5-20 seconds;

– arc protection with start-up from electric arc transducer;

– blocking of electric motor repeated start-up;

– protection from wrong alternation of phases.

The device provides remote and local management of the switch. The continuous control of serviceability of switch inclusion and disconnect circuits is carried out.

Besides the active values of the basic harmonic of three-phase currents, phase voltage, back sequence current, trebled voltage of zero sequence and active capacity are calculated in working mode. The basic measurement error of the specified values does not exceed 0.5 %. There is an opportunity of the specified parameters display on the obverse panel of the device.

Astronomical uniform time conducting and discrete information and oscillogram registration is carried out. Thus the status changes of each entrance discrete signal; start-up, operation and return of each protection; command on disconnection distribution, etc are fixed. The active current values of each stator phase are registered at emergency disconnection of the switch, i.e. digital oscillographing of emergency processes is carried out; the entrance analog signal deviations for given response level with fixing of date and time for each event are registered.

The information interchange with the monitoring and management system and external computer is provided under the COMTRAD standard. Information interchange speed is not less than 19200 bits per second.

The device is equipped with the built - in system of self-diagnostics providing the continuous constant control of technical means, communication lines and software serviceability, and also the software and settings safety. The information on a status and work of the device is given out to the monitoring and management system, and is also displayed on the obverse panel as the light signal system.

The opportunity of diagnostics and definition of the protected electric motor and switch fulfilled resource is stipulated.

The device adjustment is carried out with the help of the built - in management board, external portable PC or from the monitoring and management system.

The device is made using modular principle in the body, is compatible with relay compartments of complete switching center cases with voltage of 6-10 kW. The protection degree is IP54, for entrance and target clips - IP21. Overall dimensions are no more than 300*300*200 mm3. Weight of the device does not exceed 7 kg. The device meets all requirements of State standard specification of Russia.

Average mean-time-between-failures is not less than 100 000 hours. Service life of the device is not less than 30 years. Keeping quality term is not less than 2 years.


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