JPH03143220A - Digital type protective controller - Google Patents

Abstract

PURPOSE:To monitor a defective current input section by simple constitution by providing the pre-stage of an analog-digital conversion section with a DC- section generating means adding the quantity of DC electricity and furnishing a DC-section generation monitor means monitoring a DC section in a digital data. CONSTITUTION:A section between an input converter 1-1 and a filter 2-11 is provided with a DC-section generating means 2-51, and a DC section is added. A DC section in a digital data taken into a digital arithmetic section 3 is adjusted at a fixed value under a sound state. A digital relay is operated in a shape including the DC section normally. When disconnection is generated between the input converter 1-1 and the filter 2-11, the output offset value of the filter 2-11 is changed. Accordingly, the DC section in the digital data is altered by the generation of a defective. The DC section is detected from the difference of the output and input of a digital filter in a DC-section extracting means 3-1. The presence of the generation of the defective is determined from the magnitude of the DC section in a DC-section generation monitor means 3-2.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a digital protection and control device, in particular, an input conversion section that converts the amount of grid electricity to a predetermined level, and an analog-to-digital conversion section. This invention relates to a digital protection control device for monitoring.

(Prior Art) The technology of applying microcomputers to protection and control devices for power systems is well known.

Specifically, digital relays that determine system faults,
These include fault locators for locating system faults and system stabilization devices for stabilizing the system.

The conventional technology will be explained below using a digital relay as an example.

FIG. 4 is a side view of the configuration of the digital relay.

The digital relay shown in the figure is composed of an input conversion section 1, an analog/digital conversion section 2, and a digital calculation section 3. The input converter 1 inputs the grid voltage or current (^-1 to A-n) to the analog/digital converter 2, so the auxiliary current transformer S is used to reduce the voltage to an appropriate voltage level. Transformer (PCT) 1-
1 to 1-n. The analog-digital converter 2 includes analog filters 2-11 to 2-1n,
Sampling hold section 2-21 to 2-2n (hereinafter S
/11) , ? It consists of a Lunaplexer 2-3 and an analog-to-digital converter 2-4 (hereinafter referred to as ^/D converter), which converts the input from the input converter 1 into a predetermined digital quantity and passes it to the digital arithmetic unit 3. In the digital calculation unit 3, the CPU performs processing such as relay determination calculation and automatic monitoring.

In the above configuration, the input converter and the analog-to-digital converter are extremely important parts in terms of protection functions, and therefore require accurate constant monitoring.

For this reason, conventionally, the following monitoring has been performed for both current and voltage inputs.

(Dikyoken Vol. 41 No. 4 “Digital Relay” P-65
) a, each phase balance monitoring max (1g, Is, Iv) α1nin
(Ia, Is, IT) <ε1(1)11a
X(VR, VB, V7) βl1lin(Vp, Vs, Vv) <ε2
(2) IIlax: Maximum value ε1 during each phase input. ε2: Sensitivity m l n: Minimum value in each phase input α, β: Coefficients, zero phase monitoring Ill +Is+ IT <ε3 (3)
V, →−V s + V T <ε4(4)ε3. ε4
: Sensitivity Equations (1) and (3) are current monitoring equations, and equations (2) and (4) are voltage monitoring equations for monitoring the input converter 1 to analog/digital converter 2.

(Problems to be Solved by the Invention) When the monitoring method described above is implemented, the following problems arise.

■ When the power flow is low, it is impossible to detect defects in the current input section. In particular, there is a high possibility that disconnection mode cannot be detected. This is (1) above.

This is because equation (3) was designed on the assumption that there is always a certain level of current.

■ In the case of single-phase input, there is no phase input to compare, so (1
) to (4) cannot be applied, and as a result, monitoring cannot be performed. For example, this applies to neutral point current, representative phase input of line voltage, etc.

Both ① and ② indicate that there are blind spots in the current digital relay monitoring system, and there is concern that it will affect the protection function, as it will not be possible to eliminate faults while they occur.

The present invention has been made to solve the above problems, and provides a digital form factor that can monitor the input converter analog-to-digital converter with high reliability.
The purpose is to provide a protection control device.

[Structure of the Invention] (Means for Solving the Problem) FIG. 1 is a functional block diagram showing the basic concept of the present invention. DC component generating means 2-51 to 2-50 that add a quantity to promote a change in the DC component when a defect occurs, and a DC component extracting means that extracts the DC component in the digital data obtained by the analog/digital changing section 2. 3-1, and a DC component generation monitoring means 3-2 that monitors whether the DC component obtained thereby is within a predetermined range of values.

(Function) The filter 2-1 is set so that the DC component contained in the digital data becomes a predetermined value in a healthy state with no defects.
If a defect occurs after the offset adjustment of 1 to 2-1n has been performed, the DC component is generated by the DC component generating means 2-51 to 2-
50, this change is detected by the DC component extraction means 3-1, and determined as a monitoring failure by the DC component generation monitoring means 3-2.

(Embodiment) The feature of the present invention is the DC component generating means 2-51, which will be explained in detail below using an example of a real square color.

FIG. 2 shows an implementation form of one channel between the input converter 1 and the S/H2-2, and the input converter 1-1 is
The filter 2-11 is composed of an auxiliary transformer Tr, and a load resistor R2, and the filter 2-11 is connected to an operational amplifier 1 and a peripheral resistor R3114.
It is composed of R5. Here, the above-mentioned DC component generating means 2
-51, a predetermined DC power supply 1 is connected between the input converter 1-1 and the filter 2-11 via a resistor R1. Here, the DC component of the digital data taken into the digital arithmetic unit 3 in a healthy state is set to a predetermined value k (k
is an arbitrary real number). Generally, this adjustment is realized by human-based adjustment of the voltage V2 applied to the resistor R5. As a result, at all times (when in good condition), the digital relay is operated with the DC component k included in the amount of grid electricity (alternating current amount). - Since a digital filter is included in the relay calculation of the digital relay and the DC component is removed, the influence of the DC component does not affect the relay function.

Next, consider a case where a defect, particularly a disconnection, occurs between the input transformer Tr and the filter Tr.

In this case, if either the Tr+ side or the filter 1 side becomes defective, equivalent to a disconnection, the magnitude of the current that was being shunted to the TrI side and the filter ^1 side via the resistor R1 changes, and the filter ^1 side becomes defective. Input voltage changes. As a result, the output offset value of the filter ^1 changes.

This results in a change in the DC voltage contained in the digital data. Also, after filter ^1 A/D
Even if the circuit between the converters 2 and 4 becomes defective (particularly in a disconnection mode), the DC component included in the digital data naturally changes.

Here, a method for realizing the DC component extraction means 3-1 is shown in FIG.

First, the analog data taken into the digital arithmetic processing section 3 has a form in which the DC component k is included in the alternating current amount, as shown in waveform A due to the above-mentioned adjustment.

A digital filter 3-1-1 removes the DC component from this signal to obtain a waveform B, and performs an amplitude calculation 3-1-2 (eg, rectification and addition method) to obtain a waveform C. As shown in waveform C, there is no DC component, and an amplitude value M of an AC waveform is obtained. On the other hand, if amplitude calculation 3-1-3 is performed as another route without going through a digital filter, a waveform is obtained. The waveform is a sum of the DC component and the amplitude value M, and by subtracting C from this 3-1-4, the waveform E, that is, the DC component k can be obtained.

In the DC component generation monitoring means 3-2, the following judgment formula is used:
Determine whether a monitoring failure has occurred.

If k-ε<E<k+ε, it is normal. If E<k-ε or if E, it is defective. However, ε≧O Here, ε is a dead zone, which is provided for the purpose of escaping the effects of temperature changes on the element. There is.

As described above, even when there is no power flow or single-phase input is taken in, by using changes in the DC component, all input channels can be monitored without leakage from the input changing part to the analog/digital changing part. can be done.

[Effects of the Invention] As explained above, according to the present invention, precise monitoring of the vicinity of the analog input section when there is no power flow, which was a blind spot in conventional monitoring methods, or when receiving single-phase input becomes possible with a simple configuration. , it has become possible to provide a highly reliable digital protection control device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic concept of the present invention, Fig. 2 is a block diagram of an embodiment, Fig. 3 is a block diagram of an embodiment of DC component extracting means, and Fig. 4 is a block diagram of a prior art. It is. 2-51 to 2-50...DC component generating means 3-1...
DC component extraction means 3-2...DC component generation monitoring means

Claims (1)

[Claims] Digital type protection that inputs the analog electrical quantity of the power system, samples and holds it at a predetermined timing, converts this held analog quantity into digital quantity, and uses the obtained digital data to perform protection control processing. In the control device, a DC component generating means adds a predetermined amount of DC electricity to a stage upstream of the analog-to-digital converter to prompt a change in the DC component when a failure occurs, and a DC component extracting means extracts the DC component from the digital data. and DC component generation monitoring means for monitoring whether the DC component obtained by the DC component extraction means is within a predetermined range of values.