GB1591499A

GB1591499A - Voltage regulation and reactive power compensation device for voltage step-down substations and power transmission lines

Info

Publication number: GB1591499A
Application number: GB8014/78A
Authority: GB
Original assignee: G N I ENERGETI I IM GB KRZHIZH
Current assignee: G N I ENERGETI I IM GB KRZHIZH
Priority date: 1978-03-01
Filing date: 1978-03-01
Publication date: 1981-06-24
Also published as: DE2811099A1; FR2425748B1; FR2425748A1; SE7802727L; DE2811099C2; SE419390B; JPS54121940A

Description

(54) VOLTAGE REGULATION AND REACTIVE POWER COMPENSATION DEVICE FOR VOLTAGE STEP-DOWN SUBSTATIONS AND POWER TRANSMISSION LINES (71) We, GOSUDARSTVENNY NAucHNo-IssLEDovATELsKY ENERGETICHESKY INSTITUTIMENI G. M.

KRZHIZHANOVSKOGO, of USSR, Moscow, Leninsky prospekt, 19, a State Enterprise organised and existing under the laws of the Union of Soviet Socialists Republics, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the distribution of electrical energy and, more particularly, to a voltage regulation and reactive power compensation device for voltage step-down substations and power transmission lines.

The problems of voltage regulation and reactive power compensation are interlinked in that compensation of a power line's reactive load brings about a change in the voltage across that line. There are a number of different types of devices intended to compensate the reactive power and regulate voltage levels at the power distribution end, in order to reduce power and energy losses in power transmission lines.

According to the present invention there is provided a voltage regulation and reactive power compensation device for voltage step-down substations and power transmission lines comprising a first capacitor bank and a controllable reactor each of which is connected in parallel with a power transmission line, and a second capacitor bank connected in series with the power transmission line between the points of connection to the power transmission line of the main capacitor bank and the controllable reactor.

A better understanding of the present invention will be had from a consideration of the following detailed description of preferred embodiments thereof, taken in conjunction with the accompanying drawing, wherein: FIG. 1 is an electrical circuit diagram of a voltage regulation and reactive power compensation device in accordance with the invention; FIG. 2 is the diagram of FIG. 1 with the capacitor banks arranged on the highvoltage side of a transformer.

Referring to the drawings FIG. 1 shows a voltage regulatio.l and reactive power compensation device 1 having its input connected to the low-voltage winding of a transformer 2 of a voltage step-down substation.

The voltage regulation and reactive power compensation device 1 comprises, in parallel connection with a power transmission line 3, a capacitor bank 4 and a controlled reactor 5. The device 1 further includes a capacitor bank 6 connected in the power transmission line 3 between the points of connection of the capacitor bank 4 and controlled reactor 5.

The device 1 has its output connected to busbars 7 of the substation, wherefrom branch feeders 8. One of the feeders 8 incorporates a voltage regulation and reactive power compensation device 9 which is similar to the device 1.

In another version of the proposed device, FIG. 2 shows a voltage regulation and reactive power compensation device 10 in accordance with the invention, wherein the capacitor banks 4 and 6 are placed on the high-voltage side of the transformer 2.

Placing both capacitor banks 4 and 6 on the high-voltage side of the transformer 2, or placing the single capacitor bank 4 on the high-voltage side of the transformer 2 may be convenient with the capacitor banks 4 and 6 being composed of individual capacitors placed in series and in parallel with one another. The choice between the device 1 of FIG. 1 and the device 10 of FIG.

2 is largely dependent upon the type of capacitors although the device 1 of FIG. 1 enables the transformer 2 to be relieved from the reactive load current.

The device 1 permits for regulation of voltage across the busbars 7 of the step-down substation. If the power demands by consumers supplied through the feeders 8 are not simultaneous it is necessary to complement the control device 1 with the selective voltage regulation and reactive power compensation device 9 arranged at the distribu tion end of one or several of the feeders 8.

The circuitry and principle of operation of the device 9 are similar to those of the device 1.

The principle of operation of the voltage regulation and reactive power compensation device 1 (FIG. 1) is as follows. The shunt capacitor bank 4 compensates the reactive component of the current through the power transmission lines 3 and thus ensures an economically reasonable reduction in power losses in the line 3; it also accounts for a slight increase in the voltage at the point of connection of this capacitor bank 4.

The device l is an improvement of the shunt capacitor bank 4 operating alone, whereupon the losses in the line 3 can only be minimized by having the capacitor bank 4 controlled and composed of a number of switchable sections. In addition,. if use is made of the capacitor bank 4 alone, the voltage across the load proves to be inadequate.

The capacitor bank 6 is used for series capacitive compensation and accounts for a rise in the voltage across the busbars 7 of the substation which is normally proportional to the reactive component of the load current flowing through the capacitor bank 6. Voltage is therefore increased without any time lag with respect to a change in the load and the lower the power factor of the load, the higher the rise in the voltage across the busbars 7.

The controlled reactor 5 augments the voltage rise, provided for by the series capacitive compensation bank 6, and also controls the voltage rise in accordance with a predetermined program. The voltage rise control is effected by changing the power consumed by the reactor 5, whereby the reactive component of the current flowing through the capacitor bank 6 changes accordingly. In order to increase the voltage across the busbars 7, it is necessary to increase the capacity of the reactor 5. This does not increase power losses in the line 3, due to an appropriate selection of the capacity of the shunt capacitor bank 4.If the power factor of the load is relatively low and the voltage rise, produced by the capacitor bank 6 as the reactive current of the load flows therethrough, is sufficient to meet the load requirements the capacity of the controlled reactor 5 is reduced to a minimum by an automatic regulator (not shown). In the case of a maximum load and a high power factor, when the voltage rise produced by the capacitor bank 6 is insufficicnt to meet the load requirements, the capacity of the controlled reactor 5 is automatically increased, which brings about a proportional rise of voltage. By appropriately controlling the reactor 5, the voltage at the output of the device 1 can be regulated with respect to both reactive and in-phase components of the load current, as well as with respect to other parameters.The device 1 is an improvement over only the capacitor bank 4 and controlled reactor 5 connected in parallel with the power transmission line 3, the increase in voltage across the load being insufficient to meet maximum load requirements; moreover, the increase in the voltage is reduced and the capacity of the controlled reactor 5 increased; the capacity of the capacitor bank 4 and the controlled reactor 5, selected so as to ensure a desired voltage level, is in excess of the total capacity of the capacitive elements of the device 1. A change in the total reactive power of the device 1, effected by means of a continuous adjustment of the capacity of the controlled reactor 5, makes it possible to dispense with discrete adjustment of the capacity of the shunt capacitor bank 4.By having the function of the reactor 5 performed by a magnetization-controlled reactor or a thyristor-switched reactor, the device 1 is made static, i.e. devoid of any movable parts. Such a device is highly reliable and makes permanent maintenance personnel redundant.

The devices 9 and 10 (FIG. 2) operate in the same manner as the device 1.

Thus the proposed voltage regulation and reactive power compensation device provides for simultaneous voltage regulation and reactive power compensation. The device performs effectively despite considerable changes in the load and despite the power factor value of the load, which may be close to unity.

WHAT WE CLAIM IS: 1. A voltage regulation and reactive power compensation device for voltage step-down sub-stations and power transmission lines, comprising a first capacitor bank and a controllable reactor, each of which is connected in parallel with a power transmission line, and a second capacitor bank connected in series with the power transmission line between the points of connection to the power transmission line of the main capacitor bank and the controllable reactor.

2. A voltage regulation and reactive power compensation device as claimed in claim 1 wherein the first capacitor bank is a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. tion end of one or several of the feeders 8. The circuitry and principle of operation of the device 9 are similar to those of the device 1. The principle of operation of the voltage regulation and reactive power compensation device 1 (FIG. 1) is as follows. The shunt capacitor bank 4 compensates the reactive component of the current through the power transmission lines 3 and thus ensures an economically reasonable reduction in power losses in the line 3; it also accounts for a slight increase in the voltage at the point of connection of this capacitor bank 4. The device l is an improvement of the shunt capacitor bank 4 operating alone, whereupon the losses in the line 3 can only be minimized by having the capacitor bank 4 controlled and composed of a number of switchable sections. In addition,. if use is made of the capacitor bank 4 alone, the voltage across the load proves to be inadequate. The capacitor bank 6 is used for series capacitive compensation and accounts for a rise in the voltage across the busbars 7 of the substation which is normally proportional to the reactive component of the load current flowing through the capacitor bank 6. Voltage is therefore increased without any time lag with respect to a change in the load and the lower the power factor of the load, the higher the rise in the voltage across the busbars 7. The controlled reactor 5 augments the voltage rise, provided for by the series capacitive compensation bank 6, and also controls the voltage rise in accordance with a predetermined program. The voltage rise control is effected by changing the power consumed by the reactor 5, whereby the reactive component of the current flowing through the capacitor bank 6 changes accordingly. In order to increase the voltage across the busbars 7, it is necessary to increase the capacity of the reactor 5. This does not increase power losses in the line 3, due to an appropriate selection of the capacity of the shunt capacitor bank 4.If the power factor of the load is relatively low and the voltage rise, produced by the capacitor bank 6 as the reactive current of the load flows therethrough, is sufficient to meet the load requirements the capacity of the controlled reactor 5 is reduced to a minimum by an automatic regulator (not shown). In the case of a maximum load and a high power factor, when the voltage rise produced by the capacitor bank 6 is insufficicnt to meet the load requirements, the capacity of the controlled reactor 5 is automatically increased, which brings about a proportional rise of voltage. By appropriately controlling the reactor 5, the voltage at the output of the device 1 can be regulated with respect to both reactive and in-phase components of the load current, as well as with respect to other parameters.The device 1 is an improvement over only the capacitor bank 4 and controlled reactor 5 connected in parallel with the power transmission line 3, the increase in voltage across the load being insufficient to meet maximum load requirements; moreover, the increase in the voltage is reduced and the capacity of the controlled reactor 5 increased; the capacity of the capacitor bank 4 and the controlled reactor 5, selected so as to ensure a desired voltage level, is in excess of the total capacity of the capacitive elements of the device 1. A change in the total reactive power of the device 1, effected by means of a continuous adjustment of the capacity of the controlled reactor 5, makes it possible to dispense with discrete adjustment of the capacity of the shunt capacitor bank 4.By having the function of the reactor 5 performed by a magnetization-controlled reactor or a thyristor-switched reactor, the device 1 is made static, i.e. devoid of any movable parts. Such a device is highly reliable and makes permanent maintenance personnel redundant. The devices 9 and 10 (FIG. 2) operate in the same manner as the device 1. Thus the proposed voltage regulation and reactive power compensation device provides for simultaneous voltage regulation and reactive power compensation. The device performs effectively despite considerable changes in the load and despite the power factor value of the load, which may be close to unity. WHAT WE CLAIM IS:

1. A voltage regulation and reactive power compensation device for voltage step-down sub-stations and power transmission lines, comprising a first capacitor bank and a controllable reactor, each of which is connected in parallel with a power transmission line, and a second capacitor bank connected in series with the power transmission line between the points of connection to the power transmission line of the main capacitor bank and the controllable reactor.

main capacitor bank and the second capacitor bank is an auxiliary capacitor bank.

3. A voltage regulation and reactive power compensation device as claimed in any preceding claim substantially as hereinbefore described with reference to the accompanying drawings.