RU2491557C1 - Method to determine components of full resistance of grounding device - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: method to determine components of full resistance of a grounding device comprising an electric circuit, in which a DC source with the help of an electronic key is connected via a shunt with an investigated grounding device, and with the second inlet - with a remote current electrode, suggests measurement with the help of a memorising oscillograph of voltage drop on a shunt u₁(t) and difference of potentials u(t) between the point of current input into the grounding device and the remote potential electrode. At the same time using data of the produced oscillogram they determine instantaneous current value and potential in the circuit at the moment of ending of the linear growth area of the grounding device potential I₁, the set value of current I₂, the initial value of voltage U₀ and the set value of voltage U₂ between the grounding device and the potential electrode, spreading resistance R_{gd spr}, resistance of the grounding device Z_{gd full}, and resistance of the interface metal-soil Z_s are determined according to the following ratios: $$R_{gdspr}=\frac{\left|U_1-U_0\right|}{I_1},$$

$$Z_{gdfull}=\frac{\left|U_2-U_0\right|}{I_2},$$

Z_s=Z_{gd full}-Z_{gd spr}.

EFFECT: expansion of functional capabilities by control of grounding device resistance parameters.

3 dwg

Description

The invention relates to a measurement technique and can be used to determine the resistance of the grounding device and its components: resistance to spreading of the grounding device and the resistance of the metal-soil interface.

Closest to the proposed is a method of measuring the resistance of the grounding device by the method of an ammeter and a voltmeter (RD-153-34.0-20.525-00. Guidelines for monitoring the state of the grounding devices of electrical installations. M: SPO ORGRES, 2000. 64 p.), According to which the source a sinusoidal voltage is connected between the grounding trigger and the remote current electrode, the current in the circuit and the potential are measured relative to the remote potential electrode. The resistance of the grounding device is calculated as the ratio of the potential difference between the grounding device and the potential electrode to the current in the circuit.

, $${\text{R}}_{\text{zu}}=\frac{{\text{U}}_{\text{zu}}}{\text{I}}$$

,

where U _zu is the potential difference between the grounding device and the remote potential electrode, V;

I - current in the circuit, A.

The disadvantages of this method are the inability to determine the components of the resistance of the grounding device.

The purpose of the invention is the determination of the components of the resistance of the grounding device.

To achieve the goal in the proposed method for determining the components of the impedance of a grounding device containing an electric circuit in which a direct current source is connected via a shunt to the studied grounding device and a remote current electrode, the voltage on the shunt is measured with a storage oscilloscope when the key is closed u ₁ (t) and potential difference u (t) between the point of current input into the grounding device and the remote potential electrode, according to the data obtained They determine the spreading resistance R _zu , the resistance of the metal-soil interface Z _g and the resistance of the grounding device Z _{zu are determined} by the following ratios:

, $$R_{s\mathrm{at}R\mathrm{but}\mathrm{from}t}=\frac{\left|U_{\mathrm{one}}-U_0\right|}{I_{\mathrm{one}}}$$

,

, $$Z_{s\mathrm{at}P\mathrm{about}ln}=\frac{\left|U_2-U_0\right|}{I_2}$$

,

Z _gr = Z _{zu full} -Z _{z ost} ,

where t ₀ , t ₁ - the moments of the beginning and end of the region of linear growth of the potential of the grounding device, ms;

t ₂ - the moment of the end of the transition process, s;

I ₁ is the current value at time t ₁ , A;

I ₂ - steady-state current value, A;

U ₀ - stationary potential of the grounding device. AT;

U ₁ - voltage value at time t ₁ , V;

U ₂ - steady-state voltage value at time t ₂ , V.

Figure 1 presents a functional diagram of a device that implements measurements by this method, figure 2 is a waveform of voltages on the shunt and grounding device.

The device contains a direct current source 1, key 2, shunt 3, oscilloscope 4, current electrode 5, potential electrode 6.

Installation works as follows:

When the key 2 is closed and the source 1 is turned on, current I appears in the circuit. The voltage drop u ₁ (t) on the non-reactive shunt 3 is registered by the first channel of the oscilloscope 4. The oscillogram determines the value of current I ₁ at the end of the linear potential growth region and the steady-state value I ₂ by the following ratios:

, $${\text{I}}_{\text{one}}=\frac{{\text{U}}_{\text{t1}}}{{\text{R}}_{\text{w}}}$$

,

, $${\text{I}}_{\text{2}}=\frac{{\text{U}}_{\text{t2}}}{{\text{R}}_{\text{w}}}$$

,

where R _W - the resistance of the shunt, Ohm;

U _t1 - voltage value on the shunt at time t ₁ , V;

U _t2 is the voltage value on the shunt at time t ₂ , V;

t ₀ , t ₁ - moments of the beginning and end of the linear growth area of the potential of the grounding device, ms;

t ₂ - the moment of the end of the transition process, s.

The change in the potential of the grounding device at the current input point relative to the remote potential electrode is recorded by the second channel of the oscilloscope 4.

With the help of the measured values, the spreading resistance R _zu is determined, the resistance of the grounding device Z _{zu full} and the resistance of the metal-soil interface Z _g according to the formulas:

, $$R_{s\mathrm{at}R\mathrm{but}\mathrm{from}t}=\frac{\left|U_{\mathrm{one}}-U_0\right|}{I_{\mathrm{one}}}$$

,

, $$Z_{s\mathrm{at}P\mathrm{about}ln}=\frac{\left|U_2-U_0\right|}{I_2}$$

,

Z _gr = Z _{zu full} -R _{zu rust} ,

where t ₀ , t ₁ - the moments of the beginning and end of the region of linear growth of the potential of the grounding device, ms;

t ₂ - the moment of the end of the transition process, s;

I ₁ is the current value at time t ₁ , A;

I ₂ - steady-state current value, A;

U ₀ - stationary potential of the grounding device, V;

U ₁ is the voltage value at time t ₁ , V;

U ₂ - steady-state voltage value at time t ₂ , V.

In the described method, the resistance of the grounding device is replaced by the existing equivalent circuit (Burgsdorf V.V. Grounding devices of electrical installations / V.V. Burgsdorf, A.I. Yakobe. M., 1989, 400 pp.), Which contains the resistance of the elements of the grounding device Z _el , the resistance of the metal-soil interface Z _g and the resistance to spreading of direct current R s _Rast . The resistance of the elements of the grounding device Z _{el is} relatively less than the rest of the components, so its value can be neglected (figure 3).

This method allows you to determine the components of the resistance of the grounding device.

Claims (1)

A method for determining the components of the impedance of a grounding device, comprising an electric circuit in which a direct current source is connected via a shunt to the test grounding device and a remote current electrode via a shunt, measuring the voltage drop across the shunt u ₁ (t) and the potential difference using a storage oscilloscope u (t) between the point of current input into the grounding device and the remote potential electrode, characterized in that according to the data of the obtained oscillograms, instantaneous e value of current and potential in the circuit in the end region of the linear growth potential grounding device I _1, the steady current value I _2, the initial value of the voltage U ₀ and a voltage steady-state value U ₂ between the ground connection and a potential electrode spreading resistance R _{zu tensile} resistance grounding device Z _{ZU full} and the resistance of the metal-soil interface Z _g is determined by the following ratios:
$$R_{s\mathrm{at}R\mathrm{but}\mathrm{from}t}=\frac{\left|U_{\mathrm{one}}-U_0\right|}{I_{\mathrm{one}}},$$

$$Z_{s\mathrm{at}P\mathrm{about}ln}=\frac{\left|U_2-U_0\right|}{I_2},$$

Z _gr = Z _{zu full} -Z _{z rast} .

Images