Power Diagnostics Solutions

70 Kirova street, suite 403, Perm, 614000, Russia Phone/fax +7 (342) 212-84-74, 212-91-93 www.dimrus.ru www.dimrus.com

Vesta

System for vibro-acoustic monitoring

of core and winding clamping pressure

of high-voltage transformers

Сore and winding clamping pressures of power high voltage transformers defines dynamic endurance of windings to short circuit currents, which can run through transformer in the alarm mode. Сore and winding clamping pressures decrease under the influence of mechanical shocks during transportation and installation, gradual insulation aging in operating conditions, repeated thermal processes. The clamping pressure checking in the service could be very important.

Most of the existing diagnostics systems of winding clamping pressure are needed to

deenergize and disconnect high-voltage line of monitored transformer. Only the expert system “Vesta” allows defining condition of winding and core clamping pressure by using vibration of transformer tank surface.

The expert software “Vesta” is based on the transformer mathematical model, which has only two vibration sources - core and windings (only active elements). In accordance with transformer model, only magnetic core vibrates in the no-load mode. The winding vibration is adds in the load mode. If winding is good pressed, it vibrates in the frequency 100 (120) Hz. If winding or core clamping pressure is less rate, vibration spectrum will have highest harmonics which are multiple of 100 (120) Hz - 200, 300, …, 1000 Hz.

It is necessary to make vibration measuring in the range up to 1000 Hz on the transformer tank surface in 12 special points for the expert program operation. These points are placed in front of high and low borders of phase transformer windings on the HV and LV transformer tank side (6 on HV side + 6 on LV). It is necessary to make vibration measuring in 2 transformer operation mode – in the no-load mode and maximum load mode.

Vibration measurements are made by

portable analyzer of vibrating signals “Korsar+” which is a part of the “Vesta” system delivery set. Vibration sensor is fixed on the transformer tank surface by the magnet. It is more convenient to install vibration sensor by insulating rod, which usually is on the substation.

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Power Diagnostics Solutions

70 Kirova street, suite 403, Perm, 614000, Russia Phone/fax +7 (342) 212-84-74, 212-91-93 www.dimrus.ru www.dimrus.com

Information about transformer tank vibration in the measuring process is saved in the device memory. The device memory is enough for saving vibration more than 40 transformers. Then data from device is transmitted to the computer and saved in the database of the expert software “Vesta”.

Winding and transformer magnetic core clamping pressure quality diagnostics is made in the automatically mode by the expert software “Vesta”. User chooses only 2 measurements in deferent modes of the monitored transformer.

Operation results of diagnostics software are graphically showed on the computer screen with marking out defects zone by «traffic lights» colors.

Designed special coefficients of condition are used for quantitative assessment of clamping pressure. It allows unifying diagnostics conclusions for all types of transformers.

The following coefficients are calculated in r.u. for each sensor location: • The coefficient of winding compression KM; • The coefficient of core compression KC; • The coefficient of compression along leakage flux paths KK; • The total compression coefficient KT. Borders of monitoring parameters technical condition is defined by the following:

If value of coefficients is not more than 0.9 this zone has good condition.

If it is less than 0.9 but more than 0.8 this zone has warning condition.

If it is less than 0.8 this zone has alarm condition. It is necessary to start thinking about possible ways to improve transformer condition.

The “Vesta” software automatically forms reports about active elements pressure quality for monitored transformer. This report contains source vibration information, drawings and you can print this report.

The “Vesta” software has build-in special expert part for diagnostics of technical condition transformer cooling system by vibrating parameters.

Measuring of oil-pumps vibration is made by the “Korsar+” device, which is a part of delivery set. Result of software operation is report about oil-pumps bearing condition, electric motor condition and oil-pump impeller condition.

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