JPS5917389B2 - live wire insulation meter - Google Patents

Description

[Detailed Description of the Invention] No. 0 The present invention is mainly intended for use under low voltage,
The present invention relates to an insulation deterioration display method capable of measuring and displaying insulation resistance under DC operating voltage and displaying various alarms.

The measurement method using a conventional insulation meter is as follows! There are 5 drawbacks.

(1) With manual insulation meters, there are variations in the applied voltage, which causes variations in the accuracy of insulation resistance measurements.With battery-powered insulation meters, not only do batteries need to be replaced, but a different voltage is applied, making measurement difficult. Sometimes the power must be cut off for 10 minutes, making it impossible to freely select the measurement time.

Furthermore, in order to measure the circuit to be measured, the circuit must be cut into pieces, which is problematic in terms of time and man-hours. (2)
There is a great deal of variation in the measured values due to the effects of 15 degrees of bias or concentration, which are exponentially related to the insulation resistance value of the equipment.

(3) Until now, there has been no instrument that can accurately display measurements of wiring, rotor, and overall insulation deterioration in DC circuits.

The present invention was made to eliminate such conventional drawbacks, and its feature is that an ammeter is connected between the positive and negative wiring and the ground to measure the maximum and minimum values of the current, and based on the measured values. and detecting insulation deterioration of each positive and negative wire and the rotor in the circuit individually by performing calculations and comparing with various allowable insulation resistance values determined in advance, and displaying and alarming the various insulation resistance values. Even if the insulation has not deteriorated enough to issue a warning, if it is dangerous overall, a comprehensive insulation deterioration display is displayed as a forecast.

The present invention will be described below with reference to the drawings. FIG. 1 shows a basic equivalent circuit for explaining the principle of the method of the present invention. Same figure! Here, P and N are the positive and negative wiring of the DC circuit, E is the earth, r is the earth short circuit protection resistance, A is the ammeter, Rp is the positive insulation resistance, and RN is the negative insulation resistance. .
Next, in the basic circuit above, the leakage current 1 due to the insulation resistance value
The analysis results of the basic relationship between insulation deterioration and insulation deterioration and the principle of the method of the present invention based on this will be explained.

The equivalent circuit for measuring insulation leakage current 1 in the case of FIG. 1 is as shown in FIG. Therefore, in r<Rp,RN(1), VO is the voltage between PN, and I represents insulation deterioration on the N side.

In order to distinguish it from rotor insulation deterioration, which will be discussed later, wiring insulation deterioration is indicated as follows.

From equation (2), it can be seen that is a constant current (
(Since RN is a value specific to the wiring), now let RNO be the VO guideline for insulation resistance deterioration, and ? =B (3)
RNO and Solepa, IMIN≧B
When (4) occurs, it is determined that the RN has deteriorated.

Since IMIN is also proportional to VO, it is best to turn off this judgment operation when VO becomes extremely low.

Next, FIG. 4 shows an equivalent circuit of a rotor system such as a generator and a motor as shown in FIG. 3.

In this case, Rp is the insulation resistance value and RR is the rotor resistance. The measurement equivalent circuit for the maximum and minimum currents 1 MIN and IMAX is shown in FIG. Then, if the voltage at the deterioration point that changes with the rotation of the rotor is V, then equations (6), (7), and (8)
From X9), the following relationship holds true.

From formula (6), IAVA + INAVA Therefore, replacing the formulas (substitutes) with formulas (7), (8), and (9), 00) formula A
O is a formula for only the rotor and insulation resistance.

Therefore, if the limit is RR-RRO, I
When R≧CO3), it can be determined that the rotor insulation has deteriorated.

Further, in the present invention, a comprehensive deterioration is displayed as a danger prediction display when the insulation of both the wiring and the rotor is slightly deteriorated, but the indication is not reached.

As mentioned in the rotor system section, 1711−11υ Therefore, when the limit is set as D, When this happens, it can be determined that the overall insulation has deteriorated.

Also, when actually setting B, C, and D, use B-2C-DO.
5) is common sense. This is because there is no need to distinguish between the insulation strength of the wiring and the rotor, and the wiring system actually includes the commutator winding and the compensation winding of the rotor.

At this time, if a rotor failure or wiring failure indication is displayed, a general insulation deterioration indication will always appear. Next, the measurement error of the instrument implementing the method of the present invention will be discussed. (1) Consider a case where the protective resistance r cannot be ignored with respect to the leakage impedance.

Suppose now.

Then, set .

As mentioned earlier, when MIN≧B, an indication of insulation deterioration on the N side appears, but let's examine what kind of error this causes when Rp becomes smaller.

At this time, as shown in Figure 6, since Rp (5r) is connected in parallel, in the formula (self), IMIN≧B-01V
When the temperature becomes 0, an indication of insulation deterioration appears, so rearranging the formula (self) gives 0.01 (Rp-1-RN) + R
When p = 10 (KΩ), RN≦5 (MΩ) Rp-1KΩ
), RN≦900 (KΩ), that is, the combination of Rp and RN in case of defective operation is as shown in FIG.

Therefore, as long as Rp does not drop extremely in practical terms, RN is sufficient.
Deterioration can be displayed.

Moreover, at this time, the setting is the same as RpO=10 (MΩ), so if P and N are switched, an insulation failure on the P side will always be displayed.

(2) In the case of a multi-rotor system, a large number of motors are usually connected to a DC circuit.

However, since they are not all rotating at exactly the same electrical angle, this instrument can detect the difference in these fluctuations and provide an indication of rotor malfunction. This instrument can respond at a speed of μSec to find the difference. In the case of each rotor system, when a rotor failure indication appears, it is best to isolate each rotor from the circuit and ultimately determine which rotor is defective.

As is clear from the above explanation, according to the present invention, various excellent effects as described below can be obtained.

(1) Since insulation resistance can be measured under operating voltage, there is no problem in terms of time and man-hours. (2) Under operating voltage, the structural arrangement that affects insulation is different due to the operation of the equipment and the thermal expansion of equipment, so there is a point where it is meaningless to measure insulation when the power is stopped, as with conventional measurement methods. All such points will be resolved.

(3) Since the temperature of the equipment is considered to be almost constant under the operating voltage, there is little variation in the insulation resistance value, which makes maintenance and management of the insulation easier.

(4) Equipment generally has no problem in practical use as long as it has sufficient insulation value under the operating voltage.

Since the bracket insulation meter according to the method of the present invention can display the insulation value itself under the operating voltage, this judgment can be made easily and maintenance management can be made easier. (5) Since measurement is performed without using an internal power source, there is no need to replenish batteries as in the past.

(6) Comprehensive insulation deterioration of wiring, rotor, etc., which did not exist in the past, can be displayed without error in the settings.

[Brief explanation of drawings]

Fig. 1 is a basic equivalent circuit diagram for explaining the principle of the method of the present invention, Fig. 2 is a measurement equivalent circuit diagram for the case of Fig. 1, Fig. 3 is a circuit diagram of the rotor system, Figs. Figure 5 is a measurement equivalent circuit diagram at the time of measurement, Figure 6 is an equivalent circuit diagram for explaining measurement error of the method of the present invention, and Figure 7 is Rp and R in the case of defective operation.
It is a figure showing the combination of N. P: Positive side wiring, N: Negative side wiring, E: Earth, A: Ammeter, r: Earth short circuit protection resistor.

Claims (1)

[Claims] 1. In an ungrounded DC circuit including a rotor and having a line voltage V_0, (a) an ammeter is connected between the positive wiring and the ground to determine the maximum current value I_N・_M_A_X and the minimum value I_N;・＿M
(b) Connecting an ammeter between the negative side wiring and the ground to measure the maximum current value I_P・_M_A_X and the minimum current value I_P・_M_I_N; (c)
When I_N・_M_I_N>V_0/R_N_O with respect to the predetermined allowable insulation resistance value R_N_O of the negative side wiring, outputting an insulation deterioration signal for the negative side wiring; (d) the predetermined allowable insulation resistance R_P_O of the positive side wiring; For I_P・_M
When _I_N>V_0/R_N_O, output the insulation deterioration signal of the positive side wiring, (e) I_R=(I_N・_M_A
_X-I_N・_M_I_N)/2=(I_P・_M_
Find A_X-I_P・_M_I_N)/2, (
f) To output a rotor insulation deterioration signal when IR≧V_0/2R_R_O for a predetermined allowable insulation resistance value R_R_O of the rotor, (g) For a predetermined allowable current value D, I_N・_M_A_X ≧D or I_P・_M_A_X≧
At the time of D, it consists of outputting a general insulation deterioration signal, and (h) displaying and alarming each insulation deterioration according to the output of each of the above-mentioned signals. 1. A method for indicating insulation deterioration under live wires, characterized in that a value is set in advance to indicate danger when the insulation has deteriorated to such an extent that the insulation deteriorates to such an extent that the insulation deteriorates to the extent that the insulation deteriorates to the extent that the insulation deterioration is insufficient for a child to issue an insulation deterioration signal.