JPH0444492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device for a static protective relay.

Generally, electromagnetic protective relays (hereinafter referred to as electromagnetic relays) have the advantage of not requiring a DC power source because the relay itself is constructed to operate in the event of an accident. However, in recent years, electromagnetic relays have been considered to be replaced by static protective relays (hereinafter referred to as static relays) made of transistors and the like due to their characteristics, large size, and maintenance aspects. Static relays are formed from electronic circuits such as transistors and computers, so
It cannot operate unless power is supplied to the electronic circuit. Therefore, a DC power source is required. This DC power supply is installed in power plants and large-scale substations to operate circuit breakers, disconnectors, transformer touch engineers, etc. It is convenient to use. However, DC power supplies are rarely installed in small-capacity customers or substations. Due to this relationship, a DC power source must be created in order to install a static relay at the above-mentioned customer. For example, this means:
DC power can be obtained from a DC power supply device at a distant power plant or large-scale substation using a long line. Figure 1 is a schematic diagram of the system realized by applying this method to a loop system. In the figure, AC is a large-scale substation. Power lines BU ₁ and BU ₂ are connected in a loop to the bus BU connected to this substation AC. A to D are consumers, and each consumer A to D is provided with a stationary relay TRY. These relays TRY are supplied with DC power from a DC power supply device DC provided in the substation AC via DC power supply lines PS ₁ and PS ₂ . CT ₁ and CT ₂ are stationary leashes.
In the current transformer that obtains the information of TRY, this current transformer CT ₁ ,
The information signal detected by CT ₂ is a static relay TRY
is input.

DC power is supplied to the static relay configured as shown in Figure 1 above through DC power supply lines PS ₁ and PS ₂ , but since these supply lines PS ₁ and PS ₂ are relatively long, the voltage There are drawbacks such as a drop in voltage and large voltage fluctuations due to the supply to several customers (four in the figure) A to D.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a power supply device for a protective relay that can obtain DC power to be supplied to a stationary relay in the vicinity of the relay.

An embodiment of the present invention will be described below with reference to FIG. 2. FIG. 2 shows the current transformers CT ₁ ,
This shows the details of CT ₂ and the static relay TRY part. Note that since the current transformers CT ₁ and CT ₂ have the same configuration, only the current transformer CT ₁ will be described in FIG. 2. R, S, and T are three-phase power lines, and these three-phase power lines R, S, and T are equipped with information detection current transformers for ground fault relays.
ZCT, and short circuit relay information detection current transformers CTR and CT _T are provided on the power line _R phase and T phase. These current transformers _CTR and CT _T. A first auxiliary current transformer AUX ₁ , AUX ₂ , AUX ₃ is provided on each secondary side of the ZCT.
On the secondary side of each of the first auxiliary current transformers AUX ₁ , AUX ₂ , AUX ₃ are resistors R ₁ , R ₂ ,
Connect R ₃ in parallel to their secondary sides. This resistance
A varistor for overvoltage protection is connected to R ₁ , R ₂ , and R ₃ in parallel.
VS ₁ , VS ₂ , and VS ₃ are connected. One end of each secondary side of the first auxiliary current transformers AUX ₁ , AUX ₂ , AUX ₃ is commonly connected, and the other end is connected to a rectifier Rf ₁ , with the polarity shown.
Commonly connected via Rf ₂ and Rf ₃ . A smoothing capacitor C and a Zener diode ZD are connected in parallel to both common connection points. Both ends of capacitor C and Zener diode ZD are constant voltage circuits.
Connected to AVR. The output voltage of the constant voltage circuit AVR is determined by the central processing unit that makes up the static relay TRY.
It is supplied to the CPU, multiplexer MPX and analog-to-digital converter A/D. The multiplexer MPX has second auxiliary current transformers ACT ₁ , ACT ₂ ,
Protection information is entered via ACT ₃ . O/E is an opto-electrical converter, and protection output data is sent out via this converter O/E.

FIG. 3 is a circuit diagram showing details of the first auxiliary current transformer AUX _1. The first auxiliary current transformer AUX ₁ is provided with a limiter LM consisting of a diode on the primary side, and this limiter LM is used to control the short-circuit current. This is to limit the current when a large current above a certain level occurs. Furthermore, since there is a varistor VS ₁ on the secondary side of the first auxiliary current transformer AUX ₁ , when a voltage higher than a certain level occurs on the secondary side, it is limited by the varistor VS ₁ .
Overvoltage is not applied to the rectifier Rf ₁ or the capacitor C.

Next, the operation of the above embodiment will be described. When the load current flowing through the three-phase power lines R, S, and T exceeds a predetermined value, a predetermined current is obtained on the secondary side of the first auxiliary current transformers AUX ₁ and AUX ₂ . This current flows through the resistances R ₁ and R ₂
, and a voltage is generated across it. This voltage is rectified by rectifiers Rf ₁ and Rf ₂ , smoothed by a smoothing capacitor C, and becomes a DC voltage stabilized by a Zener diode ZD.
The DC voltage obtained in this way is applied to a constant voltage circuit.
It is supplied to the AVR for further stabilization and then supplied to the static relay TRY.

The DC voltage obtained for the load current is the fourth
As shown in the figure, it has been confirmed through experiments that a predetermined DC voltage +V can be obtained if the load current is 1A or more. As shown in Fig. 4, when the load current becomes 1A or less, the specified DC voltage +V cannot be obtained, but protection relays, not just static relays TRY, do not need to function in the above conditions. No particular trouble will occur. However, if an accident occurs during a no-load state, it must function as a protective relay, but in this embodiment, DC power is obtained by the flow of the fault current, so this power source is used. The static relay TRY becomes operable and provides reliable protection. For example, DC power can be obtained in either a three-phase short circuit accident or a two-phase short circuit accident. Furthermore, even in the event of a ground fault, if a current of about 1A flows through the secondary side of the current transformer ZCT, a DC voltage of +V can be obtained, as is clear from FIG. As a result, protection against short circuits and ground faults can be ensured.

As described above, according to the present invention, the DC power supply to the static relay is rectified by converting the current from the current transformer that obtains the information of the protective relay, and the rectified voltage is stabilized. Since the power is supplied to the static relay, stable DC power can be reliably obtained from the load current, short circuit current, and ground fault current without the need to install a DC distribution line dedicated to the static relay from a distance. This has the advantage of not reducing the reliability of DC power supply, and also provides reliable protection against various accidents.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a loop system showing a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a circuit diagram showing details of the auxiliary current transformer, and FIG. 4 is a characteristic diagram of DC voltage with respect to load current. CT _R , CT _T ……information detection current transformer for short circuit relay,
ZCT...Information detection current transformer for ground fault relay, AUX ₁ ,
AUX ₂ , AUX ₃ ...first auxiliary current transformer, _R1 , _R2 ,
R ₃ ... Resistor, Rf ₁ , Rf ₂ , Rf ₃ ... Rectifier, C ...
Capacitor, ZD...Zener diode, AVR
... Constant voltage circuit, TRY ... Static relay.

Claims (1)

[Claims] 1. A current transformer installed on the power line to obtain the information signal of the protective relay, an auxiliary current transformer installed on the secondary side of this current transformer, and a current obtained on the secondary side of this auxiliary current transformer. A current-to-voltage converter that converts the voltage into a voltage, a smoothing circuit that rectifies and smoothes the voltage obtained by the converter, and a stabilizing circuit that controls the output of the smoothing circuit to a stable voltage. A power supply device for a static protective relay, characterized in that the DC output voltage of a stabilizing circuit is supplied to the protective relay.