JPS5927166B2 - Protective relay device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective relay device that protects a power transmission line by focusing on the propagation of traveling waves on the power transmission line.

Current differential methods and phase comparison methods have been proposed as fault detection methods for protective relay devices that protect power transmission lines, but these are all based on the theory of fundamental waves of voltage and current, and the theory that power transmission lines The idea was based on the premise that it would be expressed as a lumped constant circuit.

Therefore, when a transient phenomenon occurs due to a system fault or the operation of a switch, conventional protective relay devices malfunction or malfunction during the transition from the transient state to the steady state. The drawback was that there was a high possibility that it would work.

For this reason, conventional protective relay devices have been provided with time delay characteristics and sacrificed high-speed operation characteristics to prevent the above-mentioned malfunctions and malfunctions.

This invention abandons both of the two premises of conventional protection methods, and considers traveling waves such as voltage traveling waves, current traveling waves, or energy traveling waves on the transmission line by considering the power transmission line as a distributed constant circuit. , attempts to detect faults by focusing on the fact that the flow of these traveling waves changes due to faults in power transmission lines, and is capable of high-speed fault detection, which is difficult with conventional fault detection methods based on the theory of fundamental waves of voltage and current. It was made for the purpose of

FIG. 1 shows a two-terminal power transmission line for introducing the basic principle of this invention.

In Figure 1, the power transmission line has a length of 11. It is shown as a lossless distributed constant circuit with inductance and capacitance of c, and el(t), 11(t), ex(t)
, 1x(t), e2(t), and 12(t) are the distance X from the voltage/current terminal 1 of terminal l at time t, respectively.
The voltage and current at the point and the voltage and current at terminal 2 are d
is the distance between the two ends.

According to the theory of distributed systems, ex(t) ix(t) are coupled by.

(IO2, to 7) The solution of the equation is already known, Tb:i; B6・16 "Ma extension 11" 7゛6th needle' is the traveling wave, f(t+=) is from terminal 2 to terminal 1. ■ It is a traveling wave.

is obtained.

The following equation can be obtained from equation (5).

For il and i2, the direction in which they flow from each terminal is positive.

The following equation can be obtained from equation (6).

For il and i2, the direction of inflow from each terminal is positive.

Therefore, equations (7), (8), (9), (10
), a relational expression regarding the voltage and current of terminals 1 and 2 is established.

The relational expression aυ, α2) always holds unless an abnormality such as an accident occurs inside the power transmission line, and it does not hold only when an accident occurs inside the transmission line, so it is effective for determining internal accidents for the purpose of protection. be.

In other words, if we define the quantity using 2αυ, When there is an internal accident within terminal 1 and terminal 2, When terminal 1 and terminal 2 are healthy There is a relationship between

The presence or absence of an internal accident can be determined using 61(t) of equation (13).

203) is given as a quantity that has the dimension of current, but it can also be given as a quantity that has the dimension of voltage by doubling both sides.

That is, the presence or absence of an internal accident can also be determined using ε2(t) given by.

FIG. 2 is a block diagram showing an embodiment of the protective relay device according to the present invention.

In Figure 2, 1 and 2 are terminal 1 and terminal 2, respectively.
, B1. B2 is a bus bar at terminals 1 and 2, CT is a voltage transformer that measures the grid current, PT is a voltage transformer that measures the grid voltage, 4 is a current/voltage input device, and 5 is a delay having a delay time τ. circuit, 6 is an arithmetic device, 7 is a transmitting device,
8 is a receiving device.

Next, the operation of this protective relay device will be explained.

At the terminal 1, currents 11 (t-τ) and el (-τ) measured by CT and PT with respect to time are derived to the current-voltage input device 4.

The current/voltage input device 4 actually has an analog/digital conversion circuit, converts the input signal into a digital signal, and outputs the digital signal to the delay circuit 5.

The delay circuit 5 delays the input signal by a time τ and outputs the delayed signal to the arithmetic unit 6.

On the other hand, the terminal 2 measures the current 12(t) and the voltage e2(t) at time t, and sends these measured values to the receiving device 8 of the terminal 1 using the transmitting device 7.

The arithmetic device 6 receives the current and voltage at its own end inputted from the delay circuit 5 and the current at the other end inputted via the receiving device 8.
The calculation of equation (13) is executed for the voltage, and when the calculated value is in the relationship 204), a trip command signal is output to the breaker.

Here, the physical meaning of 2dl) and (IF), which are the basic equations for internal accident determination in this invention, will be explained.

The left side of equation (11) expresses the advancing plate entering the power transmission line from terminal 1 at time t-τ in terms of voltage.

On the other hand, the right side of the equation dF) expresses the traveling wave flowing out from the terminal 2 at time t in terms of voltage.

Therefore, when comparing both sides of the equation (1 saturation), the traveling wave traveling from terminal 1 to terminal 2 on the one hand is time τ
It is understood that this indicates that terminal 2 will be reached later.

τ is the propagation time of the traveling wave, and is determined by the distance d between both terminals and the surge propagation speed V as τ2d/v.

Similarly, equation (I2) indicates that a traveling wave traveling from terminal 2 to terminal 1 at time t-τ reaches terminal 1 after time τ.

Of course, such traveling wave propagation is realized when there is no internal accident between terminal 1 and terminal 2. When an internal accident occurs, the propagation form of the traveling wave changes and Equations (11) and (12)
) no longer holds true.

This invention protects power transmission lines by focusing on the propagation form of such traveling waves.

The embodiment shown in FIG.
When using the delay circuit 5, the delay circuit 5 is provided at the terminal 2.

The delay time of the delay circuit 6 is set in consideration of the signal transmission time from the transmitting device 7 to the receiving device 8.

Furthermore, when the arithmetic unit 6 has a storage function, the delay circuit 5 can be omitted.

As mentioned above, this invention protects the transmission line by detecting changes in the propagation form of traveling waves due to internal faults in the transmission line, so the original waveforms of voltage and current in the grid can be used as they are. There are characteristics.

The formula (1υ,
(This method does not hold true for internal accidents in the protection zone, but always holds true for external accidents, so it is a perfect system for detecting internal accidents in the system.)

Therefore, according to the present invention, it is possible to completely prevent malfunctions or malfunctions of the protective relay device due to the influence of surges accompanying the opening and closing of the switch or transient phenomena during internal accidents.

As a result, the drawbacks of conventional protective relay devices can be overcome, and operation can be judged using instantaneous values, making it even better than conventional protective relay devices in terms of high-speed operation performance. A protective relay device is realized.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a power transmission line represented by a distributed constant circuit, and FIG. 2 is a block diagram showing an embodiment of a protective relay device according to the present invention. In the figure, 1, 2... terminals of power transmission lines, 4...
...Voltage and current input device, 5...Delay circuit,
6... Arithmetic device, 1... Transmission device, 8
...Receiving device, CT...Measurement current transformer, PT...Measurement transformer, el (t). e2(t)...Terminal voltage, xl(t) + 1
2(j)...Terminal current. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a device that protects the power transmission line by detecting that the propagation form of a traveling wave that propagates with a finite propagation speed between one end and the other end of the protected power transmission line changes due to an accident on the power transmission line, the above-mentioned Find the value of the traveling wave when it passes through its own end from the sum of the product of the current at its own end of the protected transmission line, the surge impedance unique to the protected transmission line, and the voltage at its own end of the protected transmission line,
The value at the other end of the traveling wave after a predetermined time period determined by the propagation speed and the distance between one end and the other end is calculated as the product of the current at the other end of the protected power transmission line and the surge impedance at the other end of the protected power transmission line. It is determined from the sum of the voltages, and the values of the traveling waves at one end and the other end are compared, and if they are not equal, a change in the propagation mode is detected, and an accident on the protected transmission line is detected. Features of protective relay device.