JP4410180B2 - Tap control method and tap control device for split transformer with tap changer at load - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a tap control method and a tap control device for a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer.

For generators installed in power plants, it is necessary to adjust the output voltage to compensate for fluctuations in the power supply voltage to suppress voltage fluctuations at power consumers at the load end and to supply high-quality power that maintains the output voltage almost constant. It is.
For this reason, the generator is provided with a transformer with an on-load tap changer (hereinafter referred to as a transformer with LTC) as voltage adjusting means for the output voltage.

  FIG. 8 is a diagram showing a configuration of a conventional general power plant. In FIG. 8, 1A (1G) and 1B (2G) are a plurality of generators (two in the figure) connected in parallel to the power transmission system L, and 2A and 2B are these two generators 1A and 1B. The two transformers with LTC, 3A, 3B connected to each other are the circuit breakers connected between the generators 1A, 1B and the transformers 2A, 2B with LTC, and 4A, 4B with each LTC. The tap control devices 5A and 5B of the transformers 2A and 2B are instrument transformers that detect the terminal voltage of each generator circuit.

  FIG. 9 is a diagram schematically showing the generator circuit shown in FIG. 8 with the turns ratio of the transformers 2A, 2B with LTC omitted, and 6A, 6B are the low-voltage windings of the transformers 2A, 2B with LTC, L1 and L2 are impedances of the low voltage windings 6A and 6B, 7A and 7B are high voltage windings of the transformers 2A and 2B with LTC, and H1 and H2 are impedances of the high voltage windings 7A and 7B.

  As described above, the conventional general power plant has a configuration in which one transformer with LTC is provided for each generator even when a plurality of generators are provided (for example, (See Patent Document 1).

A conventional tap control method in the power plant configured as described above is as follows.
First, when the generators 1A and 1B are started, the tap control device 4A or 4B shifts the tap position of the LTC-equipped transformer 2A or 2B to the determined reference tap, and fixes the generator 1A or 1B to the tap position. 1B operation is started.

Next, during operation of the generator 1A or 1B, the tap control device 4A or 4B detects the terminal voltage V _G1 or V _G2 of the generator 1A or 1B together with the tap position signal T by the instrument transformer 5A or 5B. When the terminal voltage V _G1 or V _G2 reaches the upper limit of the predetermined threshold so as to be within the specified voltage range, the LTC-equipped transformer 2A or 2B is set so as to decrease the terminal voltage V _G1 or V _G2. When the terminal voltage V _G1 or V _G2 reaches the lower limit of the predetermined threshold value, the LTC transformer 2A or 2B is set so as to increase the terminal voltage V _G1 or VG. Tap switching control is performed so as to issue a tap lowering command.

Thus, conventionally, the transformers 2A and 2B with LTC are provided for each generator 1A or 1B to perform tap control.
Japanese Patent Laid-Open No. 7-194209 (P2, right column, paragraph number [0004])

On the other hand, as a voltage adjusting means for a plurality of generators, a split transformer with a load tap changer (hereinafter referred to as a split transformer with LTC) obtained by dividing the secondary winding of the LTC transformer into a required number is used. Can be considered.
In this method, a generator is connected to each secondary winding of the split transformer with LTC, and the tap control of the split transformer with LTC is performed with one tap control device.

  However, the conventional tap control device can take only one voltage of the generator circuit as an input, and when a plurality of generators are connected to one LTC split transformer, the first generator At the start-up, there is no problem with the same control method as the conventional LTC transformer, but the second and subsequent units cannot be moved to an arbitrary tap position by the operation of the preceding generator, and voltage control is not possible. There was a problem that it could not be done.

That is, when a conventional tap control method is applied when a plurality of generators are connected to one LTC split transformer,
(1) The first generator starts operation with the reference tap, and when the second generator is operated in parallel, it is forcibly paralleled with the operating voltage of the preceding machine.
(2) The first generator and the second generator are arranged in parallel at the reference tap.
(3) Assuming operating conditions such that the first generator is in parallel at the reference tap and the second generator is producing the maximum output, the terminal voltage when the succeeding machine is parallel Guess and control the taps in parallel.
There are three possible control methods.

  However, the method (1) above may cause the terminal voltage of the generator to be out of the specified voltage range, and the methods (2) and (3) will move the tap more than necessary, resulting in the life of the tap changer. There was a problem that became short.

  The present invention has been made to solve the above-described problems of the prior art, and in a generator circuit in which a plurality of generators are connected to one LTC split transformer, without moving taps more than necessary. Provided are a tap control method and a tap control device for a split transformer with a load tap changer capable of controlling a terminal voltage of each generator to fall within a specified voltage range with one LTC split transformer. For the purpose.

  In order to achieve the above object, the invention according to claim 1 of the present invention is a tap of a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer. In the control method, before starting the generator that is subsequently started during the operation of the previously started generator among the plurality of generators, when shifting from the parallel of the generator to be subsequently started to the steady operation, Whether or not the terminal voltages of the plurality of generators are within a specified voltage range until the terminal voltage of the plurality of generators is predicted and the operation is started from the parallel of the generators to the transition to the steady operation. Judging, if the terminal voltage of the generator is not within the specified voltage range, the tap position is switched so that the terminal voltages of the plurality of generators are all within the specified voltage range. To do.

  The invention according to claim 5 is the tap control method of the split transformer with a tap changer at load having a plurality of generators connected to the low voltage winding and having one tap changer. Predict the terminal voltage of the generator to continue operation before stopping one generator among the generators in the middle, and whether the terminal voltage of the generator to continue operation is within the specified voltage range If the terminal voltage of the generator that continues operation does not fall within the specified voltage range, the tap position is switched so that the terminal voltage of the generator that continues operation falls within the specified voltage range. It is characterized by that.

  The invention according to claim 8 is a tap control device for a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer. Among the generators, before starting the generator that is subsequently started during the operation of the generator that has been started earlier, the plurality of generators when the generator is shifted from parallel to steady operation before the subsequent startup is started. Means for predicting the terminal voltage; means for determining whether or not the terminal voltages of the plurality of generators are within a specified voltage range until the generators to be subsequently started are shifted from parallel to steady operation; And a tap changer that switches the tap position so that the terminal voltages of the plurality of generators are all within the specified voltage range when the terminal voltage of the generator is not within the specified voltage range. And

  Further, the invention according to claim 9 is a tap control device for a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer. Among the generators in operation, before stopping one generator, means for predicting the terminal voltage of the generator that continues operation, and the terminal voltage of the generator that continues operation falls within the specified voltage range If the terminal voltage of the generator that continues operation does not fall within the specified voltage range, tap so that the terminal voltage of the generator that continues operation falls within the specified voltage range. It comprises a tap changer for changing the position.

  According to the present invention, since appropriate tap control of the split transformer with LTC is possible, the terminal voltage of a plurality of generators connected with one split transformer with LTC without moving the tap more than necessary. Can be controlled so as to be all within the specified voltage range.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description of the embodiment, the same components as those in the conventional LTC tap control device shown in FIGS. 8 and 9 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a diagram showing a first embodiment of the present invention. In FIG. 1, 1A and 1B are generators, 8 is a single split transformer with LTC, and a secondary of the split transformer with LTC 8 is shown in FIG. The side split windings 8a and 8b are connected to the generators 1A and 1B via circuit breakers 3A and 3B, respectively.

  9 is a tap control device for the LTC split transformer 8, 5A and 5B are instrument transformers for detecting the generator output terminal voltage, and 10A and 10B are instrument current transformers for detecting the output current of the generator output circuit. It is.

  FIG. 2 is a diagram schematically showing between the generator output terminal shown in FIG. 1 and the high voltage winding output terminal of the split transformer 8 with LTC, omitting the turns ratio of the transformer 8. Is the low voltage winding of the split transformer 8 with LTC, L1 and L2 are the impedances of the low voltage windings 11A and 11B, 12 is the high voltage winding of the split transformer 8 with LTC, and H is the impedance of the high voltage winding 12.

  Next, the LTC split transformer 8-tap control method according to this embodiment configured as described above will be described.

  The tap control device 9 stores in advance the tap position of the split transformer with LTC 8, the transformation ratio of each tap value, the impedances L1 and L2 of the low voltage windings 11A and 11B, and the impedance H of the high voltage winding 12. The operation / stop commands S1, S2 of the generators 1A, 1B, the values of the terminal voltage VG1 and the output current iG1 of the generator 1A, the values of the terminal voltage VG2 and the output current iG2 of the generator 1B, A tap position signal T indicating the tap position is captured.

  First, the generator 1A is started in advance. At the time of starting the generator 1A, the tap control device 9 shifts the tap position of the LTC split transformer 8 to the determined reference tap, and fixes the tap position to start the operation of the generator 1A.

Next, a case where the generator 1B is started during the operation of the generator 1A will be described with reference to FIG.
The generator 1A starts the generator 1B while the generator is operating at the terminal voltage V _G10 , and the output current changes from i _G20 (≈0) in parallel to i _G21 in rated operation. If the system voltage V _H is made substantially constant during the transition time, the current i _H passing through the high voltage winding 12 of the LTC split transformer 8 changes from “i _G1 + i _{G20 ≈i G21} ” to “i _G1 + i _G21 ”. Therefore, the terminal voltage V _G1 of the generator 1A changes from V _G10 to V _G11 (= V _G10 + H · i _G21 ).

Further, the terminal voltage V _G2 of the generator 1B changes from V _G20 (≈V _H + H · i _G1 ) to V _G21 (= V _G20 + (L2 + H) · i _G21 ).
Here, the system voltage VH, the terminal voltage V _G10 and the output current i _{G1 of} the preceding machine 1A, the output current i _G21 during the steady operation of the succeeding machine 1B are known, and the tap position of the split transformer with LTC, Since the transformation ratio of the tap value, the high voltage winding impedance H, and the low voltage winding impedance L2 are also known, V _G20 , V _G21, and V _G11 can be predicted by calculating using these known values.

As described above, according to the present embodiment, the taps of the split transformer with the on-load tap changer having a plurality of generators 1A and 1B connected to the low voltage windings 11A and 11B and having one tap changer. In the control method or the tap control device, among the plurality of generators 1A and 1B, the generator that is subsequently started before the generator 1B that is subsequently started during the operation of the previously started generator 1A is started. The terminal voltages V _G11 , V _G20 , and V _G21 of the plurality of generators 1A and 1B at the time of shifting from 1B parallel to steady operation are predicted and until the subsequent starter generator 1B shifts from parallel to steady operation It is determined whether or not the terminal voltages V _G11 , V _G20 , and V _{G21 of the} plurality of generators 1A and 1B are within a specified voltage range. If not, the plurality of generators are 1A, 1 The tap is switched so that the tap position is switched so that the terminal voltage of B is all within the specified voltage range.

  Thus, the single split transformer 8 with LTC can be controlled so that the terminal voltages of the plurality of connected generators 1A, 1B are all within the specified voltage range.

Next, a second embodiment of the present invention will be described with reference to FIG.
There is no essential difference between the present embodiment and the first embodiment described above. In the present embodiment, the installation positions of the instrument transformers 5A, 5B are set to the low voltage windings 8a of the split transformer 8 with LTC, The terminal voltage V _G20 of the succeeding machine 1B can be actually measured by moving between 8b and the circuit breakers 3A and 3B.

According to the present embodiment, V _G21 and V _G11 are predicted by calculating using known data as in the first embodiment, and until the subsequent starter generator 1B shifts from parallel to steady operation. In the meantime, it is determined whether or not the terminal voltages V _G21 and V _{G11 of the} plurality of generators 1A, 1B are within a specified voltage range. If not, the plurality of generators 1A, 1B are determined. The terminal voltages of the generators 1A and 1B can be all within the specified voltage range by switching the tap positions so that all the terminal voltages are within the specified voltage range.

Next, a third embodiment of the present invention will be described with reference to FIG.
In addition to the function of the first embodiment, the tap control device 9 of the present embodiment takes in output commands P1, P2 and reactive power commands Q1, Q2 of the generators 1A, 1B.
Here, the case where the generator 1B is started during the operation of the generator 1A as in the first embodiment will be described.

In addition to the function of the first embodiment, the tap control device 9 receives i _G21 (= (P2 + Q2) /) during steady operation after receiving the operation command S2, the output command P2, and the reactive power command Q2 of the generator 1B. V _G21 ) is calculated and predicted.
Thus, the single split transformer 8 with LTC can be controlled so that the terminal voltages of the plurality of connected generators 1A, 1B are all within the specified voltage range.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
6 shows the movement of the terminal voltages VG1, VG2 and the tap control device 9 when the generators 1A, 1B are both operating in the first or third embodiment of the present invention shown in FIG. 3 shows a tap control command from the first to the split transformer with LTC 8 and a tap change of the split transformer 8 with LTC.

When the terminal voltage V _G1 of the generator 1A reaches the upper threshold value VGLH at time t1, the tap control device 9 instructs to increase the tap of the split transformer with LTC 8 in order to lower the terminal voltage V _G1 of the generator 1A. Put out. However, it takes some time for the tap of the LTC split transformer 8 to be switched. When the terminal voltage VG2 of the generator 1B also reaches the upper limit VGLH at t2 during that time, the tap control device 9 locks the command to raise the tap of the LTC split transformer 8. As a result, it is possible to prevent the tap of the LTC-equipped split transformer 8 from rising two steps.
Thus, the single split transformer 8 with LTC can be controlled so that the terminal voltages of the plurality of connected generators 1A, 1B are all within the specified voltage range.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
The generator 1A stops operation of the generator 1B during operation with the terminal voltage V _G10 and the generator 1B with the terminal voltage V _G20 , respectively, and the output current changes from i _G20 during operation to i _G21 (= 0) during _{disconnection.} It is assumed that the system voltage _VH is substantially constant in a short time when the generator is disconnected. Then, since the current _{i H} that passes through the high-voltage winding 12 of the LTC with split transformer 8 is changed from the _"i G1 _{+ i G20"} to _{"i G1 + i} G21 _{= i} G1", the terminal voltage _{V G1} of the generator 1A is It changes from V _G10 to V _G11 (= V _G10 −H · i _G20 ).

According to the present embodiment, the terminal voltage VG11 of the generator 1A is predicted before the generator 1B is disconnected, and the detected terminal voltages V _G10 and V _G20 are all within the specified voltage range (V _{GLH ˜V GLL} ) is confirmed, and if not, the tap is switched and controlled so that the tap position of the LTC split transformer 8 is changed so that all are within the specified voltage range.

Thus, the single split transformer 8 with LTC can be controlled so that the terminal voltages of the plurality of connected generators 1A, 1B are all within the specified voltage range.
In the first to fourth embodiments, the generators 1A and 1B are replaced with generator motors, and the effects of the present invention can be obtained even in the pumping operation of the generator motors.

1 is a circuit diagram showing a first embodiment of the present invention. The schematic circuit diagram of the transformer which shows the 1st Embodiment of this invention. The characteristic view which shows the fluctuation | variation of the generator terminal voltage in the 1st Embodiment of this invention. The circuit diagram which shows the 2nd Embodiment of this invention. The circuit diagram which shows the 3rd Embodiment of this invention. The characteristic view for demonstrating the 3rd Embodiment of this invention. The characteristic view for demonstrating the 4th Embodiment of this invention. The circuit diagram which shows the generator circuit provided with the conventional transformer with LTC. The schematic circuit diagram of the generator circuit provided with the conventional transformer with LTC.

Explanation of symbols

1A, 1B ... Generator, 2A, 2B ... Transformer with LTC, 3A, 3B ... Circuit breaker, 4A, 4B ... Tap control device, 5A, 5B ... Instrument transformer, 6A, 6B ... Low voltage winding, 7A, 7B: High voltage winding, L1, L2: Impedance of low voltage winding, H, H1, H2: Impedance of high voltage winding, L: Power transmission system, 8: Split transformer with LTC, 8a, 8b: Secondary split winding Wire, 9 ... Tap control device, 10A, 10B ... Current transformer for instrument, 11A, 11B ... Low voltage winding, 12 ... High voltage winding, V _G1 ... Terminal voltage of generator 1A, V _G2 ... Terminal of generator 1B Voltage, i _G1 ... output current of the generator 1A, i _G2 ... output current of the generator 1B.

Claims (9)

  In a tap control method for a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer, the generator that has been started in advance among the plurality of generators Before starting the generator that is subsequently started during the operation of the generator, the terminal voltage of the plurality of generators at the time of transition from the parallel of the generators to be subsequently started to the steady operation is predicted, and the generator to be subsequently started It is determined whether the terminal voltages of the plurality of generators are within the specified voltage range until the transition from the parallel to the steady operation, and the generator terminal voltage is not within the specified voltage range. In the case, the tap control method for the split transformer with a load tap changer is characterized in that the tap position is switched so that the terminal voltages of the plurality of generators are all within a specified voltage range.   When predicting the terminal voltage of the preceding starter generator and the subsequent starter generator when the subsequent starter generator shifts from parallel to rated operation, the tap position of the split transformer with LTC, the transformation ratio of each tap value, Estimate the impedance of the low-voltage winding and high-voltage winding, the terminal voltage and output current of the preceding starter generator, and the output current during steady operation of the subsequent starter generator using known values The tap control method for a split transformer with a load tap changer according to claim 1.   3. The tap control method for a split transformer with a load tap changer according to claim 1 or 2, wherein the tap position is switched after the operation command of the generator to be subsequently started.   If the terminal voltage of multiple generators in operation is detected, and the terminal voltage of one generator does not fit within the specified voltage range and a tap change command is issued, another command will be issued until the tap position actually changes. 3. Tap control of split transformer with on-load tap changer according to claim 1 or 2, wherein the tap change command is locked even when the terminal voltage of the generator does not fall within the specified voltage range. Method.   In the tap control method for a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer, one of the plurality of generators in operation Before stopping the generator, predict the terminal voltage of the generator to continue operation, determine whether the terminal voltage of the generator to continue operation is within the specified voltage range, and continue operation When the terminal voltage of the generator is not within the specified voltage range, the tap position is switched so that the terminal voltage of the generator to continue operation is within the specified voltage range. Tap control method for split transformer with switch. 6. The tap control method for a split transformer with a load tap changer according to claim 5 , wherein the tap position is switched after a stop command for the generator to be stopped.   The tap control method for a split transformer with a load tap changer according to any one of claims 1 to 6, wherein the generator is a generator motor.   In a tap control device of a split transformer with a load tap changer having a plurality of generators connected to a low voltage winding and having one tap changer, the power generation started first among the plurality of generators Means for predicting terminal voltages of the plurality of generators when the generator to be subsequently started during the operation of the generator is shifted from parallel to steady operation of the generator to be subsequently started; Means for determining whether or not the terminal voltage of the plurality of generators is within a specified voltage range until the generator is shifted from parallel to steady operation, and the generator terminal voltage is within the specified voltage range A split transformer with a load tap changer, characterized by comprising a tap changer that changes the tap position so that all the terminal voltages of the plurality of generators fall within a specified voltage range when not within the specified voltage range. Container Loop control system.   In the tap control device for split transformer with load tap changer having a plurality of generators connected to the low voltage winding and having one tap changer, one of the plurality of generators in operation Before stopping the generator, means for predicting the terminal voltage of the generator to continue operation, means for determining whether the terminal voltage of the generator to continue operation is within a specified voltage range, When the terminal voltage of the generator that continues operation does not fall within the specified voltage range, the tap switch that switches the tap position so that the terminal voltage of the generator that continues operation falls within the specified voltage range A tap control device for a split transformer with a load tap changer.

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