JPH01107613A - Fuse blow detecting device - Google Patents

Abstract

PURPOSE:To enhance safety and controllability by controlling a primary side relay contact of a transformer, which connects to its secondary side a fuse voltage detecting element, from an output of an insufficient voltage detecting element. CONSTITUTION:A fuse blow detecting device 1 connects a zero-phase voltage detecting element OVG and insufficient voltage detecting elements UV1, UV2 respectively through three-phase detected fuses FA, FB, FC to the secondary side of voltage transformers PTA, PTB, PTC connected to three-phase power transmission lines A, B, C. A fuse voltage detecting element OV is connected to both ends of the fuse FA through a normallyopen contact CONT. In this way, for instance, when a fuse of 1-phase or 2-phase blows, because of the element OVG operative and zero-phase current detecting element OCG inoperative, a fuse blow is detected through an inhibit circuit IN-1 and an OR circuit OR. Here under no excition of a coil of an auxiliary relay RY, the primary side of a transformer TOV is disconnected from a secondary circuit of the fuse FA by the contact CONT.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuse rupture detection device for detecting the rupture of a fuse installed on the secondary side of a voltage transformer in a power system.

[Conventional technology]

Fig. 2 is a diagram showing a fuse rupture detection device for which the applicant previously applied for a patent (filed on March 2, 1986). In Fig. 2, (Al, (B), (C1) are Protection of three-phase power transmission lines, (CT^), (CTB) *
(CTc) is a current transformer (FA) installed in each phase of the power transmission line (B) and (C').

(Fn) and (F'c) are fuses to be detected, and are voltage transformers (PTM) whose primary sides are connected to each phase of power transmission lines (A), (n), and (c).

(PTB) and (PTc) are connected to the secondary side. (CB) is the power transmission i (Al, (B), (C)
This is an interrupter installed in the

(1) is a fuse blown detection device, and this fuse blown detection device includes a synthetic transformer (TA) for inputting the three-phase voltages V3, Vb, and VC and deriving the zero-phase voltage Vo.
, (TB) - (Tc), a zero-sequence voltage detection element (OVa) that detects whether the zero-sequence voltage Vo is at least a predetermined value (for example, 10% of the rated voltage), and a zero-sequence current Io that is a predetermined value. (For example, 10% of the rated current) or more, the output of the zero-sequence current detection element (OCG) and the zero-sequence voltage detection element (0Va) are positive inputs, and the output of the zero-sequence current detection element (OCG) Inhibit (IN
HIBIT) circuit (IN-1), an input voltage transformer (TOV) that introduces the voltage Vaf across one phase of the three-phase detected fuse, for example, the human phase fuse, and the voltage Vaf across the fuse to a predetermined value (for example, Consists of a fuse voltage detection element (OV) that detects whether the rated voltage is 10cm or higher, and an OR circuit (OR) that receives the inhibit circuit (IN-1) and the fuse voltage detection element (OV) as inputs. has been done.

(DZ) is a distance relay for protecting the power transmission lines (Al, CB+, (C), and when a failure occurs in the transmission line, it outputs a trip command to the circuit breaker (CB). With load current flowing through B) and (C), the voltage transformer (PTA) - (PTB), (P
Tc) secondary side fuses (FA), (Fa).

(F'c), it is assumed that a failure has occurred in the power transmission line, and the distance relay (DZ) makes an unnecessary response and outputs a trip command to the circuit breaker (CB).

Therefore, in order to prevent unnecessary response of the distance relay (DZ) as described above, a connection is made so that when the fuse blown detection device (1) is activated, an alarm is issued to the outside and the distance relay (DZ) is automatically locked. has been done.

Next, the operation of the fuse blown detection device will be explained.

Detected fuse (FA), (FB), (Fc)
When everything is normal, the fuse output side three-phase voltage va
.

vb and vc are balanced at healthy rated voltages, and zero-phase voltage vo is zero.

However, for example, voltage transformer (PTA) - (PTB)
, (PTc), when a short-circuit failure occurs in the human phase and B phase, the fuses (FA) and (FB) are blown, and as a result, zero-sequence voltage vo is generated, and the zero-sequence voltage detection element (OVG) works.

On the other hand, since no ground fault has occurred in the grid transmission lines (Al, (B), (C)), the zero-sequence current 1. is zero and the zero-sequence current detection element (OCC) is inactive. Therefore, the inhibit circuit (IN-1) outputs an output indicating that the fuse has blown.

Also, it's not a blown fuse, but a grid transmission line (A).

(Bl, (Even if a one-phase ground fault occurs in C1, the zero-sequence voltage detection element (OVa) operates, but at this time, zero-sequence current IO is generated, and the zero-sequence current detection element (OCG) Since the inhibit circuit (IN-1) also operates, no fuse blown detection output is generated.

If all three phase fuses are blown, the zero-sequence voltage V (
, does not occur, the zero-phase voltage detection element (OVa) does not operate and no output is obtained from inhibit (IN-1), but the fuse voltage detection element (Ov) operates and the OR
A blown fuse can be detected from the circuit (OR).

[Problem that the invention seeks to solve]

Since the conventional fuse blown detection device is configured as described above, for example, during maintenance, the fuse to be detected (FA) -
Even if (Fn) and (P'c) are opened in all three phases,
The transformer (
A situation occurred in which current flowed through the primary side of the voltage transformer (TOV) and the voltage on the secondary side of the voltage transformer was being output even though the fuses were open, and maintenance personnel opened the fuses for all three phases. This poses a problem in that it is dangerous and requires some kind of countermeasure when inspecting the equipment.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a blown fuse detection device that prevents current from flowing through a voltage transformer or the like in a protective relay.

[Means for solving problems]

The fuse blown detection device according to the present invention connects a zero-phase voltage detection element and an undervoltage detection element to the secondary side of a voltage transformer connected to a three-phase power transmission line through respective three-phase detected fuses, and Connecting a fuse voltage detection element via a normally open contact to both ends of at least one phase of the three-phase detected fuse,
a drive circuit that closes the contact when there is an output from the undervoltage detection element and there is no output from the zero-phase voltage detection element;
a first logic circuit that opens the contact when the fuse voltage detection element outputs an output, and continues the output of the fuse voltage detection element until the output of the undervoltage detection element is lost; and the zero-sequence voltage detection element. There is an output of 3 above.
A second logic circuit detects disconnection of the three-phase detected wire when there is no output from the zero-phase current detection element of the phase transmission line or when there is an output from the first logic circuit. It is something that

[For production]

The blown fuse detection device according to the present invention detects the voltage only at the moment when the secondary voltage of the voltage transformer connected to the three-phase power transmission line drops and there is an output from the undervoltage detection element and no output from the zero-phase voltage detection element. By closing the contacts and inputting the voltage across the detected fuse to the fuse voltage detection element, the voltage applied to the protective relay etc. when the fuse is blown can be limited to an extremely short period of time, increasing safety and ease of operation. make things better.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, in which the same parts as in Fig. 2 are given the same reference numerals,
(1) is a fuse blown detection device, and this fuse blown detection device detects three phase voltages VB and Vb.

Vc is input and the zero-phase voltage v□ and two phases (for example, B, C
Synthetic transformer (TAI) for deriving the voltage of phase)
, (TBI), (TCI), an undervoltage detection element (tJVl), (UV
2), an inhibit circuit (IN-1) which uses the output of the zero-sequence voltage detection element (OVa) as an affirmative input and the output of the zero-sequence current detection element (OCG) as an inhibition input, and the undervoltage detection element (UVI). An inhibit circuit (IN-2) as a logic circuit which takes the logical product of the outputs of With the output as one input, the output of the (ORI) and the inhibit circuit (IN-2)
) and an inhibit circuit (ORI) whose other input is the output of the AND circuit (AND) of the outputs of
A logical sum circuit (OR) whose inputs are the outputs of the AND circuit (AND) and the inhibit circuit (IN-2
) with the output of the AND circuit (AND) as the inhibit input, and the output of the inhibit circuit (IN-3) excites the coil of the auxiliary relay (RY). , transformer (TOY) -
It consists of a driver circuit (DR) that closes a contact (CONT) connected to the next side.

Next, the operation will be explained.

(b) When the fuse of one phase or two phases is blown, the zero-phase voltage detection element (
OVa) is operating and the zero-sequence current detection element (OCG) is inoperative, so the inhibit circuit (IN-1).

A blown fuse is detected through an OR circuit (OR).

At this time, the coil of the auxiliary relay (RY) is not excited, and the negative side of the transformer (TOV) is disconnected from the fuse secondary circuit at the contact (CONT).

(〒) When a one-phase ground fault occurs in grid transmission lines A, B, and C for one season.Similar to the conventional device shown in Fig. 2 above, zero-sequence voltage detection element (OVG), zero-sequence current detection element (OCG) operate together, so no unnecessary fuse blown detection output is generated.

At this time, the coil of the auxiliary relay (RY) is not excited, and the negative side of the transformer (TOV) is disconnected from the fuse secondary circuit at the contact (CONT).

If the fuse of p→3 phase is blown, the detected fuse (F
A) If −(Fs) and (Fc) are disconnected,
Since the zero-sequence voltage V(, is not generated, the zero-sequence voltage detection element (
OVa) does not operate and no output is obtained from the inhibit circuit (IN-1), but the undervoltage detection element (UVI
) and (UV2) operate together, an output is obtained from the inhibit circuit (IN-2).

At the moment the fuse breaks, the contact (CONT) is open, so
The fuse voltage detection element (OV) is not activated, therefore, an output is obtained from the inhibit circuit (IN-3), and the driver circuit (DR) energizes the coil of the auxiliary relay (RY) and its relay contact (CONT). becomes a closed circuit.

As a result, voltage across the fuse is applied to the transformer (TOV), the fuse voltage detection element (Ov) provided on the secondary side of the transformer ('rov) operates, and the OR circuit (
ORI), AND circuit (AND), OR circuit (O
A blown fuse can be detected through R).

Also, the output of the logical product circuit (AND) is input to the inhibit circuit (
Since it is in the inhibition input of IN-3), this inhibit circuit (IN-3) stops outputting at an instant.

Therefore, the coil of the auxiliary relay (RY) becomes non-energized and the contact (CONT) opens. However, the OR circuit (OR
1) By using the logical product circuit (AND), - degree logical product circuit (
AND), the inhibit circuit (IN -
Since the AND circuit (AND) output continues until the output of 2) is lost, the undervoltage detection element (
This continues until both UVI) and (UV2) become inactive.

Here, the undervoltage detection elements (UVI) and (UV2) were installed in two phases (B and C phases) other than the phase in which the fuse voltage detection element (Ov) was installed (in this example, the human phase). If the 3-phase fuse is blown due to a fault on the secondary side of a voltage transformer other than the above, current flows through the transformer (TAI) through (TOV), and therefore voltage is generated on the secondary side of the transformer (TAI), causing undervoltage detection. element (UVI), (UV
2) Depending on the setting and measurement of the zero-phase voltage detection element (OVG), the undervoltage detection element of the human phase may be inactive and the zero-phase voltage detection element (OVG) may be activated. In this case, This is because the fuse cannot be disconnected.

In addition, in the above embodiment, the fuse voltage detection element (Ov)
Under voltage element (UVI) when installed in physiognomy.

Although we have explained the case where (UV2') is provided in the B and C phases, the undervoltage element may be in one phase (for example, the B phase). If the undervoltage detection element (UVI), (UV2) and the zero-phase voltage detection element (□vG) can be coordinated with the secondary voltage of good.

〔Effect of the invention〕

As described above, according to the present invention, a relay contact is provided on the primary side of a transformer having a fuse voltage detection element connected to the secondary side, and the opening/closing of this relay contact is controlled by the output of the undervoltage element. Therefore, when the fuse is blown, the voltage applied to the protective relay etc. can be reduced for an extremely short period of time (for example, several tens of thousands of times).
0 ms), which has the effect of increasing safety and providing a fuse blown detection device with good operability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a blown fuse detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional blown fuse detection device. (Al, (nl, (c) is protected transmission −= f'
jl, (CTA), (CTB), (CTc) are current transformers, (PTA) + (PTB), (PTc) are voltage transformers, (FA), (FB), (Fc) are fuses to be detected, (OVG) is the zero-phase voltage detection element, (OC
G) is zero-phase current detection element, (OV) is fuse voltage detection element, (IN-1), (IN-2), (IN-3
) is an inhipit circuit, (ort), (ORI)
is an OR circuit, (UVI), (UV2) is an undervoltage element, (AND) is a logic circuit, (DR) is a driver circuit, (RY) is an auxiliary relay coil, and (CONT) is an auxiliary relay contact. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent Applicant: Mitsubishi Electric Corporation, ゛------L Agent: Patent Attorney 1) Hiroshi Sawa (2 others)

Claims (1)

[Claims] A zero-sequence voltage detection element and an undervoltage detection element each connected to the secondary side of a voltage transformer connected to a three-phase transmission line via a three-phase detected fuse, and a transformer connected to the three-phase transmission line. a zero-sequence current detection element provided on the secondary side of the current flow device; a fuse voltage detection element connected to both ends of at least one phase of the three-phase detected fuse via a normally open contact; and the undervoltage detection element. a drive circuit that closes the contact when there is an output of the element and there is no output of the zero-sequence voltage detection element; and a drive circuit that opens the contact when the fuse voltage detection element outputs an output, and the output of the undervoltage detection element is a first logic circuit that continues the output of the fuse voltage detection element until it is lost; and when there is an output of the zero-sequence voltage detection element and no output of the zero-sequence current detection element; A fuse blowout detection device comprising a second logic circuit that detects blowout of the three-phase detected fuse when there is an output from the circuit.