JPH01202114A - Sampling system - Google Patents

Abstract

PURPOSE:To permit a digital protective relay to function at high precision, by regulating a frequency divider according to the change of the frequency of a power apparatus, and by regulating a sampling angle. CONSTITUTION:The input of the signals of the respective phases of a power apparatus to sampling-and-holding circuits 1-3 and a frequency deviation detecting section 4 is provided. From an oscillator 12, the pulse 12a of a con stant period is applied to a frequency divider 13, and by the frequency divider 13, the pulse 12a is frequency-divided, and the output of the sampling pulse 13a of output generated by every electrical angle of 30 deg. is generated. The input of output from the frequency deviation detecting section 4 to the frequency divider 13 is provided, and the electrical angle of the sampling pulse 13a is synchronized with system frequency. The output of the respective sampling-and- holding circuits 1-3 is generated via a multiplexer 15 and an A/D converting circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to adjusting the sampling time for pulling the amount of electricity in response to changes in the frequency of a power system.

[Conventional technology]

A digital protection relay device that protects a power system obtains a predetermined function based on data obtained by sampling the amount of electricity in the power system. The data was obtained by sampling the voltage of the normal power system in electrical degrees at 30° intervals.

In conventional sampling circuits used in digital protective relay devices, the sampling pulse is a pulse generated by an oscillator that is unrelated to and asynchronous to the grid frequency.

[Problem to be solved by the invention]

Since the conventional method is configured as described above, in order to keep the accuracy of the digital protective relay device constant, it is necessary to keep the electrical angle constant according to fluctuations in the system frequency.

However, there was a problem in that it was not possible to carry out subsidy jigging in synchronization with the system frequency, and it was not possible to obtain a summing pulse that would enable the digital protective relay device to function with high precision.

This invention was made in order to solve the problems of the conventional ones as described above, and its purpose is to provide a spring method that can generate sampling pulses synchronized with the grid frequency. Means for Solving the Problems] The sampling method according to the present invention is a sampling method in which a deviation in the system frequency is detected, and the pulse width of the frequency divider is changed based on this deviation value to synchronize the sampling angle with the system frequency.

[Effect]

The frequency deviation detection section in this invention detects the deviation between a specific frequency and the system frequency, and outputs an output for causing the frequency divider to adjust the angle corresponding to the deviation value.

〔Example〕

Hereinafter, an embodiment of the present invention will be explained with reference to FIG. 1. In Figure 1, the signal V obtained from each phase of the power system
px, Vb, Vc〉Pull-hold circuit (
1), +2), (a) and frequency deviation detection section (4
).

Oscillator (1z is a constant period pulse (12a) divided by frequency divider C
131 is input to the frequency divider (131 is the pulse (12
&) and outputs approximately every 306 electrical angles in the steady state of the signals ■, Vb, and Vc.
A pulse (13a) is output.

Sampling pulse (13a) C, each sample hold circuit (1), (2), (input to +31, sample hold circuit (1), (2),
(Signals (1a), (2a) output from 81,
(3a) is multiplexed by the multiplexer (19) to become a signal (15a), which is input to the analog-to-digital conversion circuit (161). It feeds a digital converter not shown.

Next, to explain the operation. Signals Va, Vb,
Vc is the sample and hold circuit (1), (2),
(s) and the frequency deviation detection unit (4), and when the frequency of the power system has a deviation value with respect to a specific frequency, the output (4a) is input to the frequency divider Mata 3, The electrical angle is adjusted to 30' corresponding to the frequency. This Sunbrizig output (13a) has signals Va, Vb,
Used to sample and hold Vc.

In the above embodiment, the sub-jig angle is 306, but it may be 60° or any other angle.

Further, the angle adjustment of the frequency divider may be either a stepwise method or a continuous method.

In addition, the input voltages Va, Vb, and Vc are three-phase, but 1
It is also possible to use a phase, two-phase, or three-phase OR condition.
Further, when the input voltage is O (zero), no adjustment may be made, arbitrary adjustment may be made, or switching to another voltage circuit may be performed.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain sampling pulses that are periodic to the system frequency, so that the accuracy of the digital protective relay device can be maintained at a high level.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a sampling circuit showing an embodiment of the present invention, (1), (2), (8)...sample/hold circuit, (4)...frequency deviation detector, α9. ...Multiplexer.

Claims (1)

[Claims] It includes a clock transmitter, a frequency divider that receives a pulse signal from the clock transmitter and sets a sampling angle, and a frequency deviation detector. A sampling method characterized in that a frequency deviation detection section detects the amount of change and adjusts the frequency divider according to the amount of change to adjust the sampling angle.