JPS6329498B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load relief calculation device in a unit substation or the like.

Figure 1 is an explanatory diagram showing the connection and disconnection status of each system and busbar connection and disconnector in the unit substation. In Figure 1, BK ₁ to _{BK 3} are banks, B is busbars, and CB ₁ to CB ₃ is the busbar connection and disconnector, CBa,
CBb is a protective shield. Bus line connection disconnection
CB ₁ to CB ₃ and protective shield breakers CBa and CBb are the first
In the figure, white circles indicate the inserted state, cross marks indicate the disconnected state, and black circles indicate the state to be introduced. Now, assume that an accident occurs in bank BK 1 in configuration "1" shown in FIG. ₁ before the accident. Then, the cutter CBa is cut off. At this time, in order to be able to exchange power from healthy banks BK ₂ and BK ₃ , it is necessary to connect the busbar or disconnect the power.
The operator manually inputs CB ₁ to save bank BK ₁ . (After the accident of type "1" in Fig. 1) In this case, banks BK ₂ and BK ₃ are operated in parallel, so normally no cross current flows between them. In addition, in Figure 1, the protective shield
CBa and CBb open and close automatically.

Next, in the case of configuration "2" in Figure 1, before the accident, the busbar connection and disconnector CB ₃ was disconnected, but when an accident occurs in bank BK ₁ and disconnector CBa opens. Bank BK ₂ provides power interchange. However, in this case, bank BK ₂ becomes overloaded and the overcurrent relay of bank BK ₂ operates, causing both banks BK ₁ ,
Both BK ₂ will experience a power outage. To prevent this, in configuration "2", after the accident, it is sufficient to turn on the busbar connection and disconnector CB ₃ , but both banks BK ₂ and BK ₃
If there is a tap difference between banks BK 2 and BK 3, a cross current will occur between banks BK ₂ and BK ₃ when breaker CB ₃ is inserted.

In addition, in the case of configuration "3" in Figure 1, when the bridges and disconnectors CB ₁ to CB ₃ were disconnected before the accident, there was an accident in bank BK ₁ , and banks BK ₂ and BK ₃ requested for accommodation. Once this is completed, the breaker circuit breakers CB ₁ to CB ₃ are turned on (after the accident type “3” in Figure 1). At this time, if there is _a tap difference between banks BK ₂ and BK ₃ ,
There is a drawback that cross current occurs between BK ₃ . Therefore, in the case of configurations "2" and "3", there is a possibility that load relief may not be possible.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a load relief calculation device that enables load relief that compensates for cross current.

In explaining one embodiment of the present invention with reference to the drawings, first, a relief calculation that compensates for cross current will be described using mathematical formulas. In Figure 2 A and B,
The same parts as in FIG. 1 are designated by the same reference numerals. Second
Figure A shows each bank from current transformers CT ₁ to _{CT 3} before the accident.
The value when the load current of BK ₁ to _{BK 3} is detected is I ₁ to
Let's say I ₃ . Further, the bank capacities are assumed to be Y ₁ to Y ₃ . Here, when an accident occurs in bank BK ₁ , bank
Since BK ₂ and BK ₃ are healthy, the following equation is used to determine whether or not the load on bank BK ₁ can be accommodated from banks BK ₂ and BK ₃ . (However, it is assumed that the impedance drops of both banks BK ₂ and BK ₃ are equal.) ₃ 〓 ^K=1 | I _k | ≦ α (Y ₂ + Y ₃ ) ...(1) α: Overload coefficient of equation (1) The term on the left is the total load before the accident, and the term on the right indicates that the overload of healthy banks is allowed up to α (1≦α). Equation (1) no longer holds true if the shingle breakers CB ₂ and CB ₃ are inserted in a state where there is a tap difference between banks BK ₂ and BK ₃ . This is because the overload states of both banks BK ₂ and BK ₃ are different.

Here, if there is no tap difference and the cross flow Ic = 0, the load after closing the sheath breakers CB ₂ and CB ₃ is expressed by the following formula.

On the other hand, if there is a tap difference, a cross current Ic flows. This formula becomes the following formula.

However, k = Bank BK ₂ capacity / Bank BK ₃ capacity %IRi + %IXi: % leakage impedance of transformer of bank i, %e: Difference in voltage ratio expressed as a percentage of normal transformation ratio, %Ic: Cross current in percentage of the rated current of the transformer of bank BK ₂ capacity.

Due to this cross flow, equation (2) becomes equation (4).

Here bank BK ₂ is overloaded due to cross current and bank
BK ₃ overload changes.

In other words, for bank BK ₂ , |I ₂ ′| is supplied by |I ₂ ′+I _c |, and for bank BK ₃ , |
The load of |I ₃ ′| is covered by the supply of I ₃ ′−I _c |.
Therefore, if the coefficients representing the overload of banks BK ₂ and BK ₃ are respectively β ₂ and β ₃ , the following equation is obtained.

Equation (5) indicates that banks BK ₂ and BK ₃ are overloaded by β ₂ and β ₃ of the bank rated capacity, respectively, in order to cover a load α times the bank rated capacity.

Figure 3 is a vector diagram showing the influence of cross current Ic, and this cross current Ic is reactive power. Therefore, (5)
The equation becomes as shown in equation (6).

β = max (β ₂ , β ₃ ), and if β ₂ ≧ β ₃ , then (6)
From the equation, we get equation (7).

k in equation (7) is as shown in FIG.

Therefore, if the maximum overload of each bank is β, the cross current
The relief calculation that compensates for Ic becomes equation (8) from equation (1).

₃ 〓 ^K=1 ｜I _k ｜≦β/1+kΣ (healthy bank capacity) ...(8) β: Overload coefficient (constant to be set) k: Tap difference compensation coefficient Next, according to FIG. A block diagram of the embodiment will be described. Reference numeral 10 denotes a bank accident detection section, from which bank accident detection information is output. Reference numeral 11 denotes an open/close state detecting section for the busbar connections and disconnectors CB ₁ to _{CB 3} , and this detecting section 11 outputs open/close state information of the choppers and disconnectors. 12 is a bank tap position detection section, and this detection section 12 outputs tap position detection information. Each of the above detection units 10~
Each output of 12 is input to a determining section 13 which determines whether there is a cross current or not, and this determining section 13 determines whether there is a cross current or not based on the above information.

For example, form "1" shown in FIG. 1 indicates cross-flow, and form "2" and "3" indicate cross-flow if the tap positions are different. The output of the determination unit 13 is the first arithmetic unit 1
4 is input. The first arithmetic unit 14 receives an output 13a indicating no cross flow and an output 13b indicating cross flow from the determination unit 13. For example, output 13a
When input is input, k=0 shown in equation (7) is calculated, and when output 13b is input, k (tap difference compensation coefficient) is calculated. In this calculation, the cross current Ic is calculated from equation (3) using the tap difference. The calculation output of the first calculation device 14 is input to the second calculation device 15 which performs the calculation of equation (8). This second arithmetic unit 15 contains information from the load information section 16 before the bank accident obtained from the current value of the current transformer of the bank, information from the bank capacity information section 17 about the constant to be set, and information about the constant to be set. Information from the overload coefficient information unit 18 of
If it is possible to perform the calculation of equation (8) above from the output of step 4, and the second calculation unit 15 sends out a relief calculation output. As a result, power can be exchanged from a healthy bank, and the output can be used to connect or disconnect the busbar.
It is supplied to a control device (not shown) that inputs CB ₂ and CB ₃ . In this way, banks can be rescued at high speed and power outages due to overloads and cross currents can be prevented. Furthermore, when the busbar connection or disconnector is turned on, the control device for the protective shield or disconnector will not operate. Further, although the above embodiment has been described in the case of a unit substation, it can be similarly implemented in a double bus substation.

As described above, according to the present invention, there is an advantage that operation can be performed so that a healthy bank does not become overloaded after busbar connection or disconnection is made by compensating for cross current.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the connection and disconnection status of each system and bus line in the unit substation.
Figures 2A and B are explanatory diagrams for explaining the embodiment of the present invention, Figure 3 is a vector diagram showing the influence of cross current, Figure 4 is a characteristic diagram showing the tap difference compensation coefficient, and Figure 5 is a diagram showing the influence of cross current. FIG. 1 is a block diagram showing one embodiment of the invention. DESCRIPTION OF SYMBOLS 10... Bank accident detection part, 11... Open/close state detection part of the bus line connection and disconnector, 12... Bank tap position detection part, 13... Judgment part, 14... First arithmetic unit, 1
5... Second arithmetic unit, 16... Load information section, 17... Bank capacity information section, 18... Overload information section.

Claims (1)

[Claims] 1. Bank accident detection information, busbar contact/disconnection input, shear failure state information, and bank tap position detection information are each inputted, and a determination unit that determines whether or not there is a cross current based on these information; A first arithmetic device receives the information of the judgment result of the judgment section and calculates a tap difference compensation coefficient based on the capacity of both banks according to the judgment as to whether there is a cross current or not; Tap difference compensation coefficient information, load information before the bank accident obtained from the current value of the current transformer of the bank, bank capacity information of a preset constant, and overload coefficient information are each input, and based on these information, from the healthy bank A load relief arithmetic device comprising a second arithmetic device that calculates whether flexibility is possible or not.