JPH0522846A - Protective relay - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a protective relay capable of determining a power failure at high speed and with high reliability. [Structure] A decrease in power supply frequency and a decrease in power supply voltage are detected, and a power failure is determined based on this. [Effect] Compared to the conventional example in which a power failure is determined only by the power supply voltage, it is possible to determine a power failure faster and with higher reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay, and more particularly to a protective relay for determining a power failure and disconnecting a load or switching a power supply system.

[0002]

2. Description of the Related Art For example, as shown in FIG. 6, in a power receiving facility having two systems of a commercial (common) power supply 2 and a standby power supply 3, when the commercial (common) power supply 2 fails for some reason. In this case, the standby power source 3 is switched to, but in the past, in general, the undervoltage relay (UVR) 60 detects that the power source voltage has dropped below a certain level and determines that there is a power failure, and switches the power source. Or, the load is disconnected.

[0003]

However, in such a system using the undervoltage relay 60, when the load includes the power factor improving capacitor (phase advancing capacitor) 4 and the large electric motor 5, the residual voltage of the capacitor is improved. Even if a power failure occurs due to the influence of the above, it cannot be detected immediately, a delay of several 100 msec occurs, and the switching to the standby power supply is delayed. Therefore, after the completion of the switching or when the instantaneous power failure is restored for 1 to 2 seconds, the large electric motor As with the simultaneous activation of all loads such as the above, an excessively large power receiving current may be required, and there is a drawback that a trip to the power receiving point occurs due to the overcurrent.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a protective relay capable of determining a power failure with high reliability and high speed.

[0005]

In order to achieve the above object, the present invention is configured as follows.

That is, according to the present invention, in a protective relay for detecting a power failure of a power supply, a first detecting means for detecting a decrease in power supply frequency, a second detecting means for detecting a decrease in power supply voltage, and both of the detecting means. And a determination unit that determines a power failure based on the output.

[0007]

According to the above structure, since the power failure is determined by detecting the decrease in both the power supply voltage and the power supply frequency, the speed is higher and the reliability is higher than the conventional example in which the power supply voltage is used for the determination. It is possible to detect a power failure.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1, the protective relay 1 of this embodiment is provided in a two-system power receiving facility of a commercial (conventional) power source 2 and a standby power source 3, and a power failure of the commercial power source 2 will be described later. In this way, it is detected and switched to the standby power supply 3, or the load such as the phase advancing capacitor 4 and the large electric motor 5 is disconnected.

FIG. 2 is a block diagram of a main part of the protective relay 1 shown in FIG. 1. Incidentally, FIG. 2 shows a structure for one phase.

The protective relay 1 of this embodiment is connected to a supply line 6 of a commercial power source through an instrument transformer PT, and in order to detect a power failure of the commercial power source at high speed and with high reliability, It is configured as follows.

That is, the protective relay 1 of this embodiment is
First detection means 8 for detecting a decrease in the frequency of the commercial power supply given through the over-input protection circuit 7, second detection means 9 for detecting a decrease in the voltage of the commercial power supply, and outputs of both detection means 8, 9. Determination means 10 for determining a power failure of the commercial power source based on the
And a plurality of output circuits 11 to 15 for providing outputs for switching the power supply or disconnecting the phase advancing capacitor 4 and the large electric motor 5 according to the discrimination output of the discriminating means 10.

First for detecting a decrease (Δf) in power supply frequency
The detection means 8 includes a first detection unit 16 which detects that the power supply frequency has dropped by 0.5 Hz or more and a second detection unit 17 which detects that the power supply frequency has dropped by 0.25 Hz or more over 10 to 20 msec. Have

The second detecting means 9 for detecting the decrease (ΔV) of the power supply voltage has a power supply voltage of 10% for 10 msec.
It has the 1st detection part 18 which detects that it fell more than the above, and the 2nd detection part 19 which detects that it fell 6% or more.

FIG. 3 is a diagram showing the detection characteristics of the respective detecting means 8 and 9. FIG. 3A shows the power supply frequency, FIG. 3B shows the power supply voltage detection characteristics, and the vertical axis represents the ordinate. The degree of decrease in power supply frequency (Δf) and the degree of decrease in power supply voltage (ΔV) are shown, and the horizontal axis shows time (T).

As shown in FIG. 3 (A), the first detecting means 8 has two detection characteristics for detecting a decrease of the power supply frequency of 0.5 Hz or more and 0.25 Hz or more over a period of 10 to 20 msec or more. And the second detection means 9 has
As shown in FIG. 3B, it has two detection characteristics for detecting a decrease of 10% or more and 6% or more of the power supply voltage over a period of 10 msec or more.

In this embodiment, the detection characteristic of the power supply frequency is set to 0.25 Hz and the detection characteristic of the power supply voltage is set to 6% because the accuracy of the normal frequency and voltage of the commercial power supply (0.1 to 0.1. 2 Hz, 6 to 10%).

The discriminating means 10 is a means for discriminating a power failure by combining the above-mentioned four detection characteristics and for disconnecting the load or switching the power source. The discriminating means 10 is used for both the detecting means 8 and 9. A first AND gate 20 to which the outputs of the first detectors 16 and 18 are given, and a second AND gate 21 to which the outputs of the first detector 16 and the second detector 19 of both detectors 8 and 9 are given. Second detector 17 of both detectors 8 and 9
And a third AND gate 22 to which the output of the first detection unit 18 is given, and second detection units 17 and 19 of both detection means 8 and 9.
A fourth AND gate 23 to which the output of the first AND gate 20 is given, and a delay timer 24 for delaying the output of the first AND gate 20 by about 50 to 200 msec.

In this embodiment, the power supply frequency is 0.25H.
By the output circuit 15 to which the output of the fourth AND gate 23 corresponding to the decrease of z and the decrease of 6% of the power supply voltage is given, the phase advancing capacitor 4 is disconnected to accelerate the decay of the residual voltage and The output circuits 11, 12, 13, and 14 corresponding to the outputs of the gates 20, 21, and 22 determine that there is a power failure and switch the power supply and disconnect the other loads.

In this way, the power failure of the commercial power supply is determined based on the decrease in the power supply frequency and the decrease in the power supply voltage.
It is possible to discriminate a power failure at a higher speed than the conventional example in which the discrimination is made only by the decrease of the power supply voltage.

FIG. 4 is a block diagram of an essential part of another embodiment of the present invention, and the portions corresponding to the embodiment of FIG. 2 are designated by the same reference numerals.

The first detecting means 8a for detecting a decrease in the power supply frequency detects the frequency decrease of Δf1 to Δf4, respectively, and the first to fourth detecting sections 25 to 28 and the detecting sections 25 to 28, respectively.
Delay timers 29 to 32 for delaying the outputs of the delay timers 29 to 32, and a first OR gate 41 to which the outputs of the delay timers 29 to 32 are given.

On the other hand, the second detecting means 9a for detecting the drop in the power supply voltage detects the voltage drops ΔV1 to ΔV4, respectively, and the first to fourth detectors 33 to 36 and the detectors 33 to 3 respectively.
Delay timers 37 to 40 for delaying the output of 6 and a second OR gate 42 to which the outputs of the delay timers 37 to 40 are given.

FIG. 5 is a diagram showing the detection characteristics of the first and second detection means 8a and 9a. FIGS. 5A and 5C show the detection characteristics of the first detection means 8 and FIG. B) and (D) are second
The detection characteristic of the detection means 9a is shown.

The first to fourth detectors 25 of the first detector 8a
~ 28 is 10 to 20 m as shown in FIG.
1.0 Hz (Δf1), 0.75 over sec (Tf1)
Hz (Δf2), 0.5 Hz (Δf3), 0.25 to 0.2.
It detects a decrease in the power supply frequency of 1 Hz (Δf4). Each of the delay timers 29 to 32 delays the output of each of the detection units 25 to 28 for a period of 0, α2, α3, and α4, and outputs the delayed timers 29 to 32. (A), (C)
Of Tf1 to Tf4.

Therefore, the output of the first OR gate 41 of the first detection means 8a is the stepwise detection characteristic Δ of FIG. 5 (A).
Since it is represented by fa, the output of the fourth detector 28 of the first detector 8a is represented by the detection characteristic Δfb in FIG. 5 (A).

Similarly, the first to fourth detectors 33 to 36 of the second detector 9a are connected to each other as shown in FIG.
20% (ΔV1), 15% over msec (Tv1)
(ΔV2), 10% (ΔV3), and 9 to 5% (ΔV4) decrease in power supply voltage are detected. Each of the delay timers 37 to 40 delays the output of each of the detection units 33 to 36 for a period of 0, β2, β3, β4, and outputs the delay timers 37 to 40. It corresponds to Tv1 to Tv4 in (B) and (D), respectively.

Therefore, the output of the second OR gate 42 of the second detecting means 9a is the stepwise detection characteristic Δ in FIG. 5B.
The output of the fourth detector 36 of the second detector 9a is represented by the detection characteristic ΔVb of FIG. 5B.

The discriminating means 10a is for discriminating a power failure by combining the above-mentioned four detection characteristics Δfa, Δfb, ΔVa, ΔVb, and switching the load or switching the power source. , The first and second OR gates 4
A third OR gate 43 to which the outputs of 1 and 42 are given and a first OR gate 43 to which the outputs of the first and second OR gates 41 and 42 are given
An AND gate 44 and a fourth OR gate 45 to which outputs from the fourth detectors 28 and 36 of both detectors 8a and 9a are given.
And a second AND gate 46 to which the outputs of the fourth detectors 28 and 36 of both detectors 8a and 9a are applied.

The discrimination output of the discriminating means 10a is given to output relays 47 to 54 for switching the power source or disconnecting the phase advancing capacitor 4 and the large electric motor 5 or the like.

In this embodiment, the fourth OR gate 45 or the second AND gate 4 is based on the detection characteristic Δfb of the first detecting means 8a and the detection characteristic ΔVb of the second detecting means 9a.
The output relays 51 and 52 corresponding to 6 disconnect the phase advancing capacitor 4 to accelerate the decay of the residual voltage,
Detection characteristic Δfa of the detection means 8a and second detection means 9a
Output relays 47, 48 corresponding to the third OR gate 43 or the first AND gate 44 based on the detection characteristic ΔVa of
As a result of a power failure, the power source is switched and other loads are disconnected.

In this embodiment, the first and second detecting means 8
a, 9a delay timers 29 to 32, 37 to 40
Can be variably set within a range of 0 to 300 msec, and can be appropriately set so as not to perform an unnecessary operation according to a load state.

Needless to say, the detection characteristics of the first and second detection means of the present invention are not limited to those of the above-mentioned embodiments.

[0034]

As described above, according to the present invention, the power failure is determined based on the decrease in the power supply frequency and the power supply voltage. Therefore, it is faster than the conventional example in which only the power supply voltage is used, and moreover, it is faster. It is possible to determine a power failure with high reliability. As a result, even if the power source is switched, an unnecessary power receiving point trip or the like does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a power receiving facility of the present invention.

FIG. 2 is a block diagram of a main part of the protective relay of FIG.

FIG. 3 is a diagram showing the detection characteristics of the embodiment of FIG.

FIG. 4 is a block diagram of an essential part of another embodiment of the present invention.

5 is a diagram showing the detection characteristics of the embodiment of FIG.

FIG. 6 is a diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 Protective relay 8, 8a 1st detection means 9, 9a 2nd detection means 10, 10a Discrimination means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Okuda 4429 Minami Abu-cho, Ichinomiya-cho, Aso-gun, Kumamoto Prefecture Omron Aso Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A protective relay for detecting a power failure of a power source, the first detecting means for detecting a decrease in power supply frequency, the second detecting means for detecting a decrease in power supply voltage, and A protective relay, comprising: a determination unit that determines a power failure based on the outputs of both detection units.