JPS61245221A - On-load tap changer - Google Patents

Abstract

PURPOSE:To improve the reliability of an on-load tap changer by flowing a current to the load via a nonlinear resistance in a tap exchange mode to detect the voltage applied to a thyristor and giving the ON/OFF commands to the tap exchanger. CONSTITUTION:An on-load tap changer using solid state switches like thyristors 6-9 supplies the power to a load 1 from an AC power supply 5 via AC power controller 3 and 4 and a transformer winding 2 having plural taps. Here a nonlinear resistance 27 is set in parallel to the controllers 3 and 4. Furthermore a voltage detecting circuit 22 is added together with a control circuit 23, a tap rise command detecting contact 24 and a tap all command detecting contact 25. Thus the voltage applied to thyristors 6-9 are detected in a tap change mode by flowing a current to the load 1 by the resistance 27. Thus a detecting circuit for load current can be omitted and the control protection and an alarm action are possible in an abnormal action mode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an on-load tap changer using a solid state switch.

[Conventional technology]

FIG. 6 is a block diagram of a conventional on-load tap switching device using a solid state switch such as a thyristor, as disclosed in, for example, Japanese Patent Application Laid-Open No. 51-83152.

In the figure, fil is the load, (21 transformer winding with multiple taps, +31 +41 is the AC power regulator, 15
+ Iri AC power supply, (6) to (9) are thyristors, α
ω control device, 0υ current regulator, function is a potentiometer, (2) is a current transformer, Q4 is a voltage detector, Q5#-j electronic circuit, α6 (171 is a comparator, (to) α is Photoelectric coupling, (E) is a negative element, and Φη is a logic circuit. Figure 7 shows a newly created load to supplement the conventional example shown in Figure 6, published in Japanese Patent Laid-Open No. 51-83152. This is a phase diagram of voltage (Vp) and current (1p), showing the case of an inductive load, with the voltage in the direction from transformer terminals A to B being the positive direction, and the current direction from the transformer to the load being the positive direction.

Next, the operation will be explained and explained. In the conventional example, tap switching was performed by controlling the thyristors (6) to (91) as follows. That is, the thyristors (6) to t9+1d control device (10 ) is controlled by the current regulator (2).
The set value from a setter, for example a potentiometer (2), and the actual value of the load current provided by a current transformer (to) are input. A voltage detector α is prepared for detecting the zero point of the AC voltage of the power supply, and an electronic port glraB is prepared for monitoring the voltage in the same direction in the thyristors (6) to (9) of the power regulator (31f+l).Thyristor (6)-(9)
can be ignited only when the anode is at a positive potential.

In the case of power regulators +31 +41 operating in parallel, when one thyristor of the power regulators +31 +41 is fired, the other power regulator has no current, or the direction in which the newly fired thyristor flows. This is possible only for electric current. Therefore, in the case of inductive loads where voltage and current have a phase, it is possible to detect thyristors by detecting the presence or absence of current, determining the polarity, and detecting the direction of the voltage applied to the thyristor.
(9) is suitably ignited to switch to a predetermined tap. For example, if the load (11 is the phase relationship of voltage and current in Figure 7, and the power regulator f3) (4+) is not passing the load current, the thyristor (91 and (7) ) is a positive potential, and the current direction is the direction in which the current flows through the thyristors (9) and (7).At this time, by firing the thyristor (91) and the thyristor (7), the tap (c) Kuke (
B) will be selected.

On the other hand, when the tap (B) is selected in the voltage-current phase load of FIG. 7, the thyris (7) is conductive between time t1 and time t3. Between t2 and ts, put the thyristor (9) on,
The anode becomes a positive potential. At this time, for example, when a firing signal is given to the thyristor (9) at time t4, the current flows from the thyristor (7) to the thyristor (9) due to the voltage between the taps.
The current will be commutated to the tap (C>). Also, with a pure resistive load, the current will be commutated from the tap (ω) to the tap (C
), the time interval from t2 to t5 in FIG. 7 disappears, making commutation from thyristor (7) to thyrisk (9) impossible. Similarly, commutation from thyristor (6) to thyristor (8) is also not possible. Therefore, in conventional devices, in order to switch from tap (B) to tap (C), for example, all thyristors are made non-conductive during the turn-off time, and the thyristors +
After turning off 61 +71, consideration was given to firing the thyristor (8) and mechanism (91) of tap (C). If a tap is switched from tap (at) to tap (B) in a short-circuited state, there is a risk that a short-circuit between the taps will occur.

[Problem that the invention seeks to solve]

Conventional tap switching bag when loaded! ! Since it is configured as above it/'i, the voltage polarity applied to the thyristor and a current detection circuit are required, making the circuit complicated. Further, tap switching is impossible because the current detection circuit does not operate in a minute current range. Furthermore, in the case of a purely resistive load, there are problems such as the need to appropriately switch taps in consideration of turn-off time and commutation. Furthermore, if a thyristor is experiencing a short-circuit failure, there is a possibility that a short-circuit between taps may occur.

This invention was made to solve the above-mentioned problems, and it is possible to perform tap switching no matter what load is connected to the on-load tap changer. Even in the case of abnormal conditions,
We are on the verge of creating an on-load tap changer that can operate with high reliability through proper control protection and alarm operation.

Means for Solving Problem C] In the on-load tap switching device according to the present invention, a nonlinear resistor and a voltage detection circuit are connected in parallel with a solid state switch such as a thyristor, and the solid state switch is made non-conductive during tap switching. After applying the load current to the connected nonlinear resistor and confirming that the voltage is applied to the solid state switch for a predetermined period,
It makes the solid-state switch connected to the voltage tap to be switched conductive, and when the voltage detector cannot detect a voltage while the solid-state switch is not conducting for a predetermined period during tap switching, the solid-state switch is stopped; When voltage is applied to the solid state switch even after the period has passed, the solid state switch selected before the tap switching operation is operated, and when the operation is other than normal, the selective protection and alarm operation are performed. It is something.

[Effect]

The on-load tap switching device according to the present invention detects the load current by detecting the voltage that does not apply to the thyristor by passing current to the load using a nonlinear resistance when switching the tap, and appropriately giving an on/off operation command to the solid state switch. Tap switching can be performed using the same control method for any load without requiring a circuit, and highly reliable tap switching can be achieved by performing control maintenance and six alarms in the event of an abnormal operation.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, fil to (9) are the same as the above conventional one. (b) is a nonlinear resistance, and! ! It has the voltage-current characteristics shown in Figure 2. (A) is a voltage detection circuit, @ is a control circuit of the present invention, and (A) is a tap-up command detection contact, which closes the contact for a predetermined period when a tap-up command is input from an external source (not shown). Furthermore, when a tap-lowering command is received from an external source (not shown), the tap-down command detection contact closes the contact for a predetermined period of time. FIG. 3 shows the internal configuration of the control circuit (to). In the figure, (IOlJL) (
1011)) is a one-shot multivibrator circuit,
(102a) (m) (102C) Figure 4 shows the truth value of the D flip-flop circuit. (103a) (
M131)) (1(77) (ri delay circuit, (1α
a) (X)4b) (M)4C) (1041i) is a NOT circuit, (105a) ~Qo5k) is an AND circuit.

(1o6a) (106b) is a three-man OR circuit, (10B
) i 2-man OR circuit, (1o9) is NOR circuit, (
uO) is an integrator, (1n) is a comparator, (u2) is a voltage detection period discrimination circuit, and (113) and (114) are accident occurrence detectors. FIG. 5 is an explanatory diagram when an embodiment of the present invention is applied to lower tap switching in the case of an inductive load.

Next, the operation will be explained. First, the voltage-current characteristics h of the nonlinear resistor (b) in FIG. 2 will be explained.

This non-linear resistor also serves as protection for the thyristor (81+91).■2 is the limiting voltage for the thyristor (81i).
The value is selected to be lower than the reverse # voltage of 9+. This is the peak value of Void inter-tap pressure on V days. When a voltage of this value is applied to a nonlinear resistance gradient, a current flows through the nonlinear resistance. is a very small value and the current can be considered to be zero. Between this voltage 72.70, vO<v2...
・Kanku of formula 0 holds true. Peak value vo of voltage between taps
The tri circuit voltage Vp is about 3-chi of the 2 series. The nonlinear resistor is selected so that the voltage v2 is approximately a factor of 5 of the circuit voltage Vp.

Next, a tap switching operation under an inductive load according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. The phase relationship between the voltage Vp of the inductive load fi+ and the current ip is shown in FIG. In FIG. 3, the output (141) of the AND circuit (105j'') is a command to fire thyristors (8+ +910), and the output (142) of the AND circuit (105k) is a command to fire thyristors +61 +71. The ignition command is stopped when the spring is at the L level, and the ignition command is issued when it is at the H level.As will be explained later, in order to select the transformer tap (C) in Figure 1, the tap-up command is detected. If the contact (c) was previously operated, the AND circuit (105
The output (141) of j) is at H level. Also, the output (142) of the AND circuit (105k) is at L level. Therefore, the output (凰1) of the AND circuit (105j) gives a firing command to the thyristor (81+91), and the tap (
c3 is selected. Assume that a tap-down detection contact (not shown) is turned on at time t1 in FIG. 5 by externally applying a tap-down command (not shown) from this state. The H-level input (120) is always connected to the tap-down and tap-up detection contact (7). Therefore, the output (121) of the one-shot multivibrator circuit M (1011) remains at H level for a predetermined period. Therefore, from the truth value in Figure 4, the D flip-flop circuit (1o2a)
The output (122) of the D flip-flop circuit (1021) becomes the L level, and the output (12:S) of the D flip-flop circuit (1021) becomes the HH level. Since the input (121) of the OR circuit (1 gloss) has become H level, the output (124) has become H level, and the output (13'/
) to L level. For this reason, AND times @ (105j
)'s output (141) immediately goes to L level, and the ignition command of thyristor f81 (910) stops.
Regarding the output (131) of the circuit (1051:+), D
Since the delay circuit (103b) is connected to the output (123) of the flip-flop circuit (102b), it becomes H level after a delay of 71 hours from time point 11. After the ignition command of thyristor (8 + 191) is stopped, the load current will flow for a half cycle period of thyristor (8) or thyristor (91) power supply period at most. ~ (Choose a value greater than or equal to the sum of the maximum turn-off times of 91. From this, any thyristor will turn off after T1 time in any state. AND circuit from 11 to t4 (1o513)
The output (Ul) becomes L level. Until time t2 in FIG. 5, the load current is 1. becomes zero. At this time, thyristor (6)
Since no firing command is given to ~ (9), the thyristor (
6) ~ (91 off. For this reason, the thyristor +61
The circuit voltage Vp is about to be applied to the parallel circuit of 17) and the parallel circuit of thyristors +81 and +91. However, according to the wave characteristics of the voltage of the non-linear resistor ('4) mentioned earlier, the full load current flows through the non-linear resistor (■), and as a result, the thyristor +
The voltage I/'1v11 applied to 81191 and the voltage applied to thyristor +61 (7) are limited to v2 plus stub voltage. Since the voltage vQ is only a factor of 5 of the circuit voltage vp, the effect on the load (11) due to the voltage drop applied to the nonlinear resistor (5) can be ignored for the most part. The output (125) from the mouth Wllr@ becomes H level when the peak value or more of the inter-tap voltage Vθ is detected regardless of the polarity.Therefore, it becomes H level from time t2.After this signal (125), a delay occurs. Because of the circuit (10'7), the signal (132) becomes H level with a delay of the TQ waiting time from the signal (125).12 hours is the maximum turn-off time of the thyristors (6) to (91). Therefore, the thyristor (81) is completely turned off at time 13, which is T2 time from time 1. Also, the output (132
) becomes H level. The output (136) of the AND circuit (105d) becomes H level.

On the other hand, the voltage detection period judgment circuit (n2) ld, the integrator (
110) and a comparator (1), and when the integrator output (126) input from the integrator (uO) to the comparator (ul) is greater than the comparator input (127), the output of the comparator (in) It outputs a 1l-tH level, and a small L level. The period from when the H level is input to the input of this integrator (no) until the comparator (111) outputs the H level is 72 hours or more depending on the voltage setting of the comparator input (12)). It will be 1 hour. In addition, for T and time, 12 hours is set to 1.5 times So. Therefore, in the above normal operation,
The output (12B) of the comparator (Ill) is at the L level, and the outputs (134) (129) of the AND circuit (xo5e) (1o5f) are at the L level. For this reason,
Each output (1
33) (140) company, R level. Also, N
The output (135) of the OR circuit (109) is output from the AND circuit (
105a) (+ to 105) output (130) (131
) is tl −t.

Since they are at L level until the period, they are at H level during that period. This causes the signal (125) to be L at the time 1=
level becomes H level, and the D flip-flop circuit (
102c) output (137) becomes H level.

At time 13, 12 hours after this state at time t2, O
Since the output (139) ld of R times M (1061)) and the input (136) become H level, it becomes H level. As a result of the above, at this point the output of the AND circuit (105k) (1
42) ld becomes H level, thyristor +81 +
91 is fired. Below, AND times 1B (1
The output (131) of 05b) becomes HL/PEL, and from then on, a firing command is given to the thyristor (81 (sl) to select tap (B). Tap raising operation from tap (B) to tap (C) The tap-up command detection contact is turned on when a tap-up command (not shown) is given from the outside.Hereafter, it operates in the same manner as the above-mentioned tap change-down operation to turn the tap change. .

Although the lagging phase load has been explained above, the operation is similar for phase advancing loads and pure resistance loads. Furthermore, even if the current sensor is unable to detect a minute current load, the control does not require current detection, so it goes without saying that the control will operate in the same way.

In the above embodiment, the case of tap switching due to normal operation has been described, but it will be explained that the on-load tap changer of the present invention can perform tap switching operation even when the following two assumed abnormalities occur.

If the voltage detector (a) cannot detect the voltage during period 11.14 in Figure 5, the nonlinear resistor (product) or thyristor (6
) to (9) have caused a short circuit failure, or the straddle voltage detector (
A possible cause is that the item (b) has malfunctioned. At this time, firing thyristors (6) to (91) will cause a short circuit between the taps.
-There is a risk that it may occur. Therefore, when the voltage detector (product) does not detect a voltage, the output (125) of the voltage detector (a) does not become H level, and the clock input does not enter the D flip-flop circuit u (102c). Accordingly, the D flip-flop circuit (102c
) is held at L level. With this, AND times VI! The outputs (141) and (142) of r(1o5j) (105k) are set to L level, and the thyristors (6) to (91) are not fired.In such a state, the accident occurrence detector (113 )
outputs an accident occurrence signal.

Furthermore, when the voltage detector (a) detects a voltage after the required period t2, it is possible that the thyristor +81191 Fi does not fire and the current continues to flow through the nonlinear resistor (b). Nonlinear resistors generally have low thermal resistance, so there is a risk of thermal damage if current continues to flow through them. Therefore, when the voltage detector (2) detects voltage for 15 hours longer than the T♀ period, the output of the comparator (1) (12B
) takes advantage of the fact that it reaches H level. Comparator (1
m) output (128) becomes H level, tap (C)
When switching from D7 to tap (B), the output (123) of the D7 lip-flop circuit (102b) is at H level, and the output (122) of D7 lip-flop circuit (102a) is at L level.

Therefore, the output (1
34) is at L level, and the output (129) of (105f) is at H level.
level, the output of the D flip-flop circuit (1020) (
13'7) is configured to be at H level. From the above, the output (141) of the AND circuit (105j) is at H level,
Since the output (142) of (105k) becomes L level,
The ignition signal is sent to the thyristor (81t9+) of tap (C), and the ignition signal is not sent to the thyristor +61 (71).

Also, when the voltage detector (a) detects the voltage for 73 hours while trying to switch from tap @) to tap (c), the signal (123) is L level, (122) is H level, and (134) is H level, (129) is L level, (1
3)) is set to level ■. In this case, AN
The output (141) of the D circuit (105j) is at L level, (1
Since the output (142) of 05k) becomes H level, a firing signal is sent to thyristor (6) (6), and thyristor +8
1 The ignition signal is not sent to +91. The above operation prevents secondary accidents such as short circuits between taps in both cases of raising and lowering the taps. In this state, the accident occurrence detector (n4) outputs a signal indicating the occurrence of an accident.

If an abnormal operation like the one described above occurs, it becomes impossible to perform tap switching operations after that, so as mentioned above,
Each condition is detected by an accident detector (113 x 114) and an accident signal is sent to the control room of the substation that monitors the operating status of the transformer, displaying alarms and accidents, and displaying taps at the corresponding load. Protective operations such as opening a breaker for a transformer with a switching device can be performed.

〔Effect of the invention〕

As described above, according to this invention, the load is 1! No current detection circuit is required, tap switching can be performed for any load, and appropriate control protection and alarm actions can be performed even in the event of an abnormality.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a tap switching device according to an embodiment of the present invention, FIG. 2 is a voltage-α current characteristic curve diagram of a nonlinear resistor, FIG. 3 is an internal configuration diagram of a control circuit, and FIG. Truth diagram of flip-flop,! FIG. 45 is an explanatory diagram of the lowering operation of tap switching in an inductive load by applying one embodiment of the present invention;
FIG. 6 is a structural diagram of a conventional on-load tap switching device using a solid-state switch such as a thyristor, and FIG. 7 is a phase diagram of a conventional load voltage Vp and current 1p. In the figure, ill is a load, (2) is a transformer winding with a tap, (31 (41ij) AC power regulator, (5) is an AC power supply, (6) to (9) are thyristors, +101 is a control device, αη is a current regulator, (Ll is a potentiometer, Q3 is a current transformer, α is a voltage detector, (to) is an electronic circuit, aOα′ is a comparator, (is is a 1) is a negative element, (c) is a logic circuit, (
4) is the voltage detection circuit, (to) is the control circuit, (Foundation) is the tap-up command detection contact, 翺 is the tap-down command detection contact, (
lola) (1011:+) H one-shot multivibrator circuit, (loza) Dozb) (1ozc)
HD-y lip flow circuit, (1osa) Do3
bX1o7) #- is a delay circuit, (104a) to (1o
4d) is a NOT circuit, (105a) to (105k) is an AND circuit, (106a) (106b) is a 3-person OR circuit, (10B) i is a 2-person 01R circuit, (10
9) n NOR circuit, (110) integrator, (1m
) Vi Cocoalator, (112) fl voltage detection period judgment circuit, (x13) and (114) are accident occurrence detectors, respectively. Note that the reference numeral 8 in the middle of each figure indicates the same or equivalent part.

Claims (2)

[Claims] (1) Connecting a first solid state switch to each of the plurality of voltage taps of the transformer winding, supplying power from the predetermined voltage tap to the load, and controlling the operation of the first solid state switch. For those that switch voltage taps, the first
The solid-state switch is made non-conductive for a predetermined period of time, and a load circuit current is passed through a nonlinear resistance element connected in parallel with the first solid-state switch, and the voltage detector connected in parallel with the first solid-state switch After confirming that voltage has been applied to the solid state switch for a predetermined period of time, the second solid state switch connected to the voltage tap to be switched is operated to perform tap switching, and during the non-conducting period of the first solid state switch. When the voltage detector does not detect a voltage, both the solid state switches are stopped, and the application period of the voltage applied to the first solid state switch during the non-conducting period of the first solid state switch is a predetermined period. An on-load tap changeover device, characterized in that the first solid state switch is operated when the load exceeds . (2) Connecting a first solid state switch to each of the plurality of voltage taps of the transformer winding, supplying power from the predetermined voltage tap to the load, and controlling the operation of the first solid state switch. For those that switch voltage taps, the first
The solid state switch is made non-conductive for a predetermined period of time, and a load circuit current is passed through a nonlinear resistance element connected in parallel with the first solid state switch, and a voltage detector connected in parallel with the first solid state switch is connected to the first solid state switch. After confirming that voltage has been applied to the solid state switch for a predetermined period, a second solid state switch connected to the voltage tap to be switched is operated to perform tap switching, and during the non-conducting period of the first solid state switch, the second solid state switch connected to the voltage tap to be switched is operated. When the voltage detector does not detect a voltage, or when the voltage applied to the first solid state switch is applied for a period longer than a predetermined period during the non-conducting period of the first solid state switch, a protective device or alarm is activated. An on-load tap switching device characterized by operating the device.