CN201345536Y

CN201345536Y - Transformer neutral point capacitance-resistance mixed type inhibition direct current device

Info

Publication number: CN201345536Y
Application number: CNU2009200506802U
Authority: CN
Inventors: 梅桂华; 梁文进; 刘艳村
Original assignee: TESTING INST GUANGDONG PROV POWER INDUSTRY BUREAU
Current assignee: TESTING INST GUANGDONG PROV POWER INDUSTRY BUREAU
Priority date: 2009-01-22
Filing date: 2009-01-22
Publication date: 2009-11-11
Anticipated expiration: 2019-01-22

Abstract

The utility model provides a transformer neutral point capacitance-resistance mixed type inhibition direct current device. A capacitance-resistance mixed main circuit is composed of a direct current circuit breaker, a capacitor and a resistor and is in series connection between a high pressure transformer neutral point and a transformer station ground net, a PLC program controller receives measuring signal transmitted from an alternating current mutual inductor, a Hall direct current sensor and a Hall voltage sensor, carries out logic judgement according to the size of the semaphore, and controls the close/disconnection of the direct current circuit breaker. When direct current passes through the transformer neutral point, the direct current circuit breaker is disconnected, the capacitor and the resistor are connected between the transformer neutral point and the ground net to respectively play obstruction and direct current restriction functions. Once AC failure current passes through the transformer neutral point, the direct current circuit breaker is immediately closed to guarantee that the transformer neutral point is directly grounded, thereby inhibiting the direct current from entering a high pressure transformer through the neutral point which is directly grounded, and protecting safe operation for the transformer.

Description

A kind of transformer neutral point capacitance-resistance mixed type suppresses flow directing device

Technical field

The utility model relates to a kind of electric device, is specifically related to suppress direct current and flows into high-tension transformer through directly grounded neutral point, the electric device of protection transformer safe operation.

Background technology

When HVDC (High Voltage Direct Current) transmission system is moved in the big earthed return mode of one pole, there is direct current to flow into the earth, gives near the high-tension transformer of the neutral-point solid ground of direct current grounding pole and have the distant place high-tension transformer that directly or indirectly is electrically connected to bring serious D.C. magnetic biasing problem with it from direct current grounding pole up to thousands of amperes.

The present domestic device that three types inhibition direct current inflow transformer is arranged: 1) reverse dc injection device.This device need be set up a little distant place direct current grounding pole, thus can not change the infield arbitrarily, and the engineering cost costliness.That adopts the method has " applied analysis that transformer neutral point injects reverse anti-magnetic bias direct current " (Kuai Dizheng, east china electric power, 2005.6).2) series connection small resistor device.This device is only applicable to low soil resistivity area, and when electric network composition changed, the fixed resistance value parameter of this device can not satisfy new inhibition direct current requirement.Adopt the having of the method " suppressing the series resistor measure of transformer DC magnetic bias " (Zhao Jie, Automation of Electric Systems, 2006.12); 3) electric capacity is every straight device.The method can intercept direct current inflow transformer neutral point fully.But adopted several power electronic device, made that the hardware configuration of control system and software design are all very complicated; Main assembly---capacitor, capacitive reactance under power frequency (50Hz) is chosen bigger, be about 1 ohm, when transformer neutral point flows through tens thousand of amperes interchange fault current, can produce very high voltage at the capacitor two ends, need to adopt expensive special capacitor, the insulation to transformer neutral point also is an acid test simultaneously.1 ohm of ground connection capacitive reactance of transformer neutral point also has certain influence to the zero sequence relaying protection of this transformer.Adopt the having of the method " PAC-40K suppresses transformer neutral point direct current device " ( Http:// www.epri.ac.cn/cycp/3364.html).

Summary of the invention

The purpose of this utility model proposes a kind of structure and control is all simple and reliable, and transformer neutral point capacitance-resistance mixed type easy to maintenance suppresses flow directing device, to solve three kinds of above-mentioned existing drawbacks of inhibition direct current device.

The purpose of this utility model is to realize like this, designed transformer neutral point capacitance-resistance mixed type suppresses flow directing device by a dc circuit breaker, a capacitor, resistor and electromagnetic AC current transformer, the Hall DC current sensor, Hall voltage transducer and PLC cyclelog are formed, dc circuit breaker, capacitor, serial connection was gone between high-tension transformer neutral point and the substation ground network after these three devices of resistor composed in parallel the capacitance-resistance hybrid circuit, electromagnetic AC current transformer and Hall DC current sensor are connected in the output circuit of capacitance-resistance hybrid circuit, the Hall voltage transducer is connected the two ends of capacitor, the electromagnetic AC current transformer, the detection signal input PLC cyclelog of Hall DC current sensor and the output of Hall voltage transducer, the output of PLC cyclelog is connected with dc circuit breaker, to the control signal of dc circuit breaker input control dc circuit breaker closure/cut-off.

Designed transformer neutral point capacitance-resistance mixed type suppresses in the flow directing device, and the capacitive reactance of described capacitor under power frequency (50Hz) is 0.05 ohm to 0.5 ohm; 50 times to 150 times of the power frequency capacitor value that said resistor value is a capacitor.

This transformer neutral point capacitance-resistance mixed type suppresses flow directing device can realize the following course of work: when direct current appears in transformer neutral point, dc circuit breaker 1 cut-offs, capacitor 2 and resistor 3 insert between transformer neutral point and the earth mat, play the effect that intercepts and limit direct current respectively.In case fault current appears exchanging in transformer neutral point, dc circuit breaker 1 is closed immediately, guarantees the direct ground connection of transformer neutral point.

The effect and the technical characterstic of the circuit each several part of designed transformer neutral point capacitance-resistance mixed type inhibition flow directing device are as follows:

(1) capacitive reactance of described capacitor under power frequency (50Hz) is 0.05 ohm to 0.5 ohm.When dc circuit breaker cut-offs, if transformer neutral point flows through tens thousand of amperes interchange fault current, the voltage that produces at the capacitor two ends has only thousands of volts, need not to adopt expensive special capacitor, the conventional capacitor product of producing according to GB gets final product, even the most bad situation---dc circuit breaker 1 can not be in time closed, the quality of capacitor also ability itself is can stood the interchange fault current.Simultaneously, so little capacitor value is also very little to the influence of the zero sequence relaying protection of transformer.The low capacitive reactance value of capacitor makes that the utility model and value are that electric capacity in the past about 1 ohm is compared every straight device, and operational reliability improves greatly.

(2) described resistor value is more than 30 times of capacitor power frequency capacitor value, its role is to, and when dc circuit breaker cut-off, what play a major role was capacitor, only leaks very little direct current flow from the resistor branch road; When dc circuit breaker transferred closure state to from cut-offfing state, the discharging current that resistor can the limiting capacitance device had been protected the safety of capacitor and dc circuit breaker.

(3) described electromagnetic AC current transformer is used for the alternating current of measuring transformer neutral point, and described Hall DC current sensor is used for the direct current of measuring transformer neutral point, and the Hall voltage transducer is used for the direct voltage at Measurement of capacitor two ends.

(4) described PLC cyclelog carries out logic determines according to the size of three measuring amount described in above-mentioned (3) part, output closure signal or cut-off signal and control the closure of dc circuit breaker/cut-off also can manually be controlled the state of dc circuit breaker.

The utility model can reliably suppress direct current effectively and flow into high-tension transformer through directly grounded neutral point, the safe operation of protection transformer, and have simple in structure, design and construction easily, advantage such as engineering cost is low.

Description of drawings

Fig. 1 is the circuit structure diagram that transformer neutral point capacitance-resistance mixed type suppresses flow directing device.

Among the figure: 1-dc circuit breaker, 2-capacitor, 3-resistor, 4-AC current transformer, 5-Hall DC current sensor, 6-Hall voltage transducer, 7-PLC cyclelog, control loop in the 8-dc circuit breaker 1, the 9-first neutral point ground cutter, the 10-second neutral point ground cutter.

Embodiment

Below in conjunction with accompanying drawing CONSTRUCTED SPECIFICATION of the present utility model and application are described in further detail.

Structure of the present utility model is shown in the A among Fig. 1, and main circuit is composed in parallel by dc circuit breaker 1, capacitor 2 and resistor 3, and an end is received on the neutral point of high-tension transformer by 9 series connection of the first neutral point ground cutter, and the other end is received on the substation ground network.PLC cyclelog 7 receives from three measuring components: the measuring-signal that AC current transformer 4, Hall DC current sensor 5 and Hall voltage transducer 6 transmit, size according to these semaphores is carried out logic determines, the closure of control dc circuit breaker/cut-off.

After the utility model put into operation, dc circuit breaker 1 should be in closure state.When being lower than, the transformer neutral point alternating current sets limit value for the moment, PLC cyclelog 7 judges that promptly electrical network does not have short trouble, detect the transformer neutral point DC current values again and whether be higher than setting limit value two, the words that are, signal is cut-off in i.e. 8 outputs of control loop in control dc circuit breaker 1, makes dc circuit breaker 1 transfer the state of cut-offfing to.When dc circuit breaker 1 when cut-offfing state, in case surpassing, the transformer neutral point alternating current sets limit value one, perhaps the direct voltage at capacitor two ends is lower than setting limit value three, PLC cyclelog 7 i.e. the 8 output closure signal of control loop in control dc circuit breaker 1, make dc circuit breaker 1 transfer closure state to.

Claims

1. a transformer neutral point capacitance-resistance mixed type suppresses flow directing device, it is characterized in that by dc circuit breaker (1), capacitor (2), resistor (3), electromagnetic AC current transformer (4), Hall DC current sensor (5), Hall voltage transducer (6) and PLC cyclelog (7) are formed, dc circuit breaker (1), capacitor (2), serial connection was gone between high-tension transformer neutral point and the substation ground network after these three devices of resistor (3) composed in parallel the capacitance-resistance hybrid circuit, electromagnetic AC current transformer (4) and Hall DC current sensor (5) are connected in the output circuit of capacitance-resistance hybrid circuit, Hall voltage transducer (6) is connected the two ends of capacitor (2), electromagnetic AC current transformer (4), the detection signal input PLC cyclelog (7) of Hall DC current sensor (5) and Hall voltage transducer (6) output, the output of PLC cyclelog (7) is connected with dc circuit breaker (1), to dc circuit breaker (1) input control dc circuit breaker (1) closed/control signal of cut-offfing.

2. transformer neutral point capacitance-resistance mixed type according to claim 1 suppresses flow directing device, it is characterized in that the capacitive reactance of said capacitor (2) under the 50Hz power frequency is 0.05 ohm to 0.5 ohm.

3. transformer neutral point capacitance-resistance mixed type according to claim 1 and 2 suppresses flow directing device, it is characterized in that said resistor (3) value is 50 times to 150 times of power frequency capacitor value of capacitor (2).