SU1464221A1 - Device for controlling blast fans of oil-cooled power transformers - Google Patents

Abstract

The invention relates to the power industry, in particular to oil cooled power transformers. The circuit of the invention consists in reducing the consumption of electrical energy by the blower motors. The device contains thermometric signaling devices 1 and 2 temperatures with contacts, relays 3 and 4 currents with contacts, And relay 5 times with winding and open contacts 6 with time delay for closing magnetic actuator 7 with winding and contacts 8 in the power supply circuit of electric motors for blower fans, signal relays 9 and 10. A thermometric signaling device 1 and a current relay 3 with contacts are connected in series in one circuit connected via a time relay 5 to a magnetic starter circuit 7, with the contact settings of the thermometric signal Ator 1 and relay 3 currents have the maximum allowable temperature value of the upper layers of oil and load currents in operating conditions. The setpoints of the thermometric signaling device 2 and the current relay connected in parallel to the serially connected contacts of the thermometric signaling device 1 and the current relay 3 have the maximum allowable temperature value of the upper oil layers and load currents in emergency conditions. 1 il. 89 С с S cl

Description

-t

S

one

This invention relates to power engineering, in particular to an oil cooled power transformer,

The purpose of the invention is to reduce the power consumption of fan motors blowing, increasing the reliability of the device.

The drawing shows a schematic diagram of the proposed device for three control points. . The device consists of thermometric temperature detectors with contacts and 2, current relays with contacts 3 and A, time relay 5 with winding and contacts 6 with time delay for closing magnetic actuator 7 with winding and contacts 8 in the power supply circuit of electric blowing fans (not shown), signal relays 9 and 10.

The device is powered from the power supply network of the fan motors.

The device works as follows.

When the transformer is turned on in the network and the current reaches the load and temperature of the upper layers of oil no more than acceptable seasonal values, which can last for a long time in normal operation modes with natural oil cooling, all contacts 1-4 are in the open state, time relay 5 does not work, contacts 6 are open, magnetic starter 7 is disconnected, contacts 8 are open, and therefore the blower fan motors do not work. .

The stable seasonal temperature of the operating transformer, provided by the natural cooling of the transformer oil circulating through the coolers, eliminates the wetting of its insulation due to the specified breathing, which is artificially reduced by the temperature of the oils.

Only when the load currents and the temperature of the upper layers of the oil exceed the permissible seasonal values at which the transformer with natural oil cooling in the normal operating mode can last for a long time, contacts 1 and 3 of the thermometric signaling device and the current relay, respectively, close. Relay 5

time delay of the order of 10-20 s, necessary for blocking unnecessary switching on and off of blower fan motors during short-term variations in current load (from starting currents, short circuits, etc.), closes the contacts 6 of the magnetic starter 7,

Q which includes contacts 8 in the power circuits supplying electric motors of blower fans.

When the magnitude of the settings triggered serially connected contacts

2 1 and 3 of the thermometric signaling device and the current relay selected during ... seasonality calculations, the switching frequency and electric motor operation time are very effectively reduced, which ensures not only a reduction in the electric energy consumption of the motors, but also a stable temperature mode of the transformer, excluding moisture isolation.

five

If the temperature of the upper layers of the oil reaches an emergency temperature corresponding to its maximum possible seasonal temperature for the highest allowable load without increasing it with natural oil cooling, contacts 2 of the thermometric alarm device close, the relay switches to time 5, with a specified time delay, the closure of the contacts 6 of the magnetic actuator 7, which includes the contacts 8 in the circuits of the electric motors of the blower fans.

In case of emergency current overload of the transformer before the temperature of the upper layers of oil rises, contacts 4 of the current relay close, time 5 trips with a known time delay, contacts 6 of the magnetic actuator 7 close, which include contacts 8 in the power supply circuit of the blower fan motors.

 B moments of the inclusion of contacts 2

0 and 4 of the thermometric signaling device and the current relay trigger the corresponding alarm relays 9 and 10, fixing faults in the transformer and giving signals, to the console

5 management of the need to turn off the transformer in order to eliminate accidents, identify and eliminate defects. Indicated alarm relays

0

five

0

five

9 and 10 can, if necessary, be used to automatically turn off the transformer.

The fan control device to blow oil-cooled power transformers is very high-tech due to the fact that the pickpoints of contacts 1 and 3 are set to seasonal, and the contacts 2 and 4 are emergency temperatures of the upper oil layers and current loads according to real physical processes occurring in the transformer based on their functional dependencies, both in normal and emergency modes.

The proposed protective device is very constructive — the benefits of the proposed control scheme, ensuring its operability in any, both joint and individual modes of transformer parameters. The protective device provides an effective increase in the reliability of the transformers due to a decrease in the degree of moisture of the insulation, a reduction in the power consumption for blowing, a more economical use of the operating life of electric motors for blower fans and switching equipment, and a reduction in the number of failures of electric motors due to frequent switching-on weather conditions.

For example, on the basis of the calculation formula, for transformers the setpoint 3 of the contacts of the current relay 3 is determined, equal to 0.7 ots „, (where IHOM is the rated load current A). The design setting of the contact closure 1 of the thermometric detector is 70 ° C in summer and 55 ° C in winter. Regarding the design settings for the contact closures 4 and 2 of the current relay and the thermometric alarm device, they are

1.1 „“ .. and 85 ° С in summer and 65 ° С

PERMITTED

 NOAL HALF-lh-n- - - -

respectively.

Calculations show when controlling fan operation with

The proposed device, the actual economic efficiency of the invention is expressed in reducing the level of damage to power transformers due to the reason of dampening insulation, reducing electrical energy consumption for technological needs, ensuring uninterrupted power supply to consumers, reducing the duration of fan operation, which averages an annual maximum. 2-3 hours a day. For 32 MB-A transformers. The reduction in electricity consumption for blow-down per year is approximately 5,470 kWh. Also, maintenance and repair costs are reduced by reducing wear of the air handling unit.

Claims (1)

Invention Formula The fan control unit blows oil-cooled power transformers, containing parallel-connected circuits, one of which contains a series-connected thermometric signaling device and a current relay, the other a thermometric signaling device, and a third a current relay, all circuits are connected through a time relay to a magnetic starter circuit characterized in that, in order to reduce the consumption of electrical energy by blower motors, to increase the reliability of the device, it is equipped with two signal relays, one of which are included in the thermometric signaling circuit, the other in the current relay circuit, the setpoints of series-connected thermometric signaling device and current relay have the maximum allowable temperature value of the upper oil layers and load currents in operating modes, and the settings of the thermometric signal indicator and current relay of other circuits have the maximum allowable value temperature of the upper layers of oil and load currents under emergency conditions.