JP3041207B2 - Oil-filled transformer insulation diagnostic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation diagnosis apparatus for an oil-filled transformer in which the insulation diagnosis of the oil-filled transformer is performed without power interruption (under a live line).

[0002]

2. Description of the Related Art Insulation management of a distribution transformer installed in an electric room of a building or the like has recently been performed using a device capable of performing insulation diagnosis under a live line. FIG. 6 is a block diagram showing a non-power failure insulation diagnosis device for electric equipment disclosed in, for example, Japanese Patent Application Laid-Open No. 4-208868. In FIG. 6, 1 is a bus, 2 is a device to be diagnosed as a power receiving / transforming facility device to which power is applied from the bus 1, 3 is an adjacent power receiving / transforming device that is simultaneously powered by the bus 1, 4 is a ground wire, and 5 is a ground wire. A clamp-type transformer clamped to the ground wire 4 of the device under diagnosis 2; 6 a high-frequency power supply; 7 a disconnector; 8 a bus of a drop cable for supplying power to the bus 1 via the disconnector 7; 1
0 is a clamp type current sensor that bundles cables, 11
Is a measuring unit.

In the non-interruptible insulation diagnostic apparatus for electric equipment configured as described above, when the clamp-type transformer 5 magnetically coupled to the ground wire 4 of the equipment under test 2 is excited by the high-frequency power supply 6, A high-frequency voltage V _S is induced at the point a, and a leakage current Ix flows to the power supply side via the lead-in cable 9 via the insulation resistance Rx and the capacitance Cx of the device under diagnosis 2. The current can be detected by the current sensor 10 which is collectively clamped. As shown in the vector diagram of FIG. 7, the measuring unit 11 that inputs the high-frequency voltage V _S and the leakage current _IX outputs a current component I _RX in phase with the high-frequency voltage V _{S serving} as a reference vector, and π / 2.
Discriminated from the leading current component I _CX and finally the dielectric loss tangent ta
nδ, insulation resistance R _X and capacitance C _X are displayed.

[0004]

SUMMARY OF THE INVENTION The above-mentioned conventional apparatus is not active.
Insulated electrical equipment in the form of a line are possible measure, although this order provides many benefits, the insulation resistance R _X obtained by this apparatus is for AC, is conventionally up to this device appears There is a problem that it is difficult to perform a trendy insulation management that matches the two because it is different from a DC insulation resistance by a megger or the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the prior art, and converts an AC insulation resistance obtained by an insulation diagnosis under a non-power failure into a DC insulation resistance to obtain a DC insulation resistance. An object of the present invention is to obtain an insulation diagnosis device for an oil-filled transformer, which can also obtain a DC insulation resistance and can manage the insulation resistance tendency without restriction of a power failure.

[0006]

An oil-immersed transformer insulation diagnostic apparatus according to the present invention is provided by exciting a transformer magnetically coupled to a ground wire of an oil-immersed transformer as a device to be diagnosed with a high-frequency power supply. A measuring unit that detects a high-frequency voltage induced in the ground line and a leakage current flowing out to the power supply side via the oil-immersed transformer and performs insulation diagnosis of the oil-immersed transformer based on the detected values. The oil-immersed transformer insulation diagnostic device provided with an oil temperature detector that detects the oil temperature of the oil-immersed transformer, and as the measurement unit, a DC insulation resistance value with respect to the oil temperature of the oil-immersed transformer. A memory in which a value of the ratio of the AC insulation resistance is stored in advance, and a first arithmetic unit for obtaining the AC insulation resistance and the capacitance of the oil-immersed transformer based on the detected values of the high-frequency voltage and the leakage current And the oil temperature detected value by the oil temperature detector and the above The value of the ratio of the DC insulation resistance and AC insulation resistance value corresponding to the value of the capacitance obtained by the first arithmetic unit read out from the memory, the first from the value of the ratio
And a second calculating unit for converting the AC insulation resistance value obtained by the calculation unit into a DC insulation resistance value to obtain a DC insulation resistance value.

[0007]

In the insulation diagnostic apparatus for an oil-immersed transformer according to the present invention, the ratio of the DC insulation resistance value to the AC insulation resistance value with respect to the oil temperature of the oil-immersed transformer is previously stored in a memory in the measuring unit. The oil temperature detector detects the oil temperature of the oil-immersed transformer,
The first arithmetic unit in the measuring unit obtains the AC insulation resistance value and the capacitance of the oil-immersed transformer based on the detected values of the high-frequency voltage and the leakage current, and the second arithmetic unit calculates the oil temperature detector. The value of the ratio between the DC insulation resistance value and the AC insulation resistance value according to the oil temperature detection value and the capacitance value obtained by the first arithmetic unit is read out from the memory, and the value of the ratio is read from the memory. The AC insulation resistance obtained by the insulation diagnosis under no power failure is converted to the DC insulation resistance by calculating the DC insulation resistance by converting the AC insulation resistance obtained by the operation unit 1 into the DC insulation resistance. As a result, a DC insulation resistance can be obtained even without a power failure, and the trend of the insulation resistance can be managed without restriction of the power failure.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a configuration diagram showing an insulation diagnosis device for an oil-filled transformer according to one embodiment of the present invention. In FIG. 1, the same parts as those in the conventional example shown in FIG.
A is an oil-immersed transformer that is a device to be diagnosed as a substation equipment to be charged from the bus 1, 3 is an adjacent substation that is simultaneously charged by the bus 1, 4 is a ground line, 5 is an oil-filled A clamp type transformer clamped to the ground wire 4 of the transformer 2A, 6
Is a high-frequency power supply, 7 is a disconnector, 8 is a bus of a drop cable that supplies power to the bus 1 via the disconnector 7, 9 is a drop cable,
Reference numeral 10 denotes a clamp-type current sensor that bundles cables.

Reference numeral 12 as a new configuration is an oil temperature detector for detecting the oil temperature in the oil-immersed transformer 2A, and 13 is magnetically coupled to the ground line 4 of the oil-immersed transformer 2A by the high-frequency power source 6. Of the high frequency voltage V _S induced at the point a of the ground line 4 by the excitation of the clamped transformer 5 and the current sensor 10
DC in terms of its AC insulation resistance R _AC with obtaining an AC insulation resistance R _AC on the basis of the detected value and the detected value the oil temperature by the oil temperature detector 12 of the leakage current Ix to the DC insulation resistance R _DC by This is a measuring unit that enables the evaluation in which the insulation resistance value R _{DC is} obtained and the AC insulation resistance value R _AC is compared with the DC insulation resistance value R _DC .

Here, as shown in FIG. 2, the measuring unit 13 previously stores the value of the ratio α between the DC insulation resistance value R _DC and the AC insulation resistance value R _AC with respect to the oil temperature T of the oil-immersed transformer 2A. The AC insulation resistance value R _{AC of the} oil-filled transformer 2A is determined based on the stored memory 13a, the high-frequency voltage V _S induced at the point a of the ground line 4, and the leakage current Ix detected by the current sensor 10.
And a first calculating unit 13b for calculating the capacitance C _X and an oil temperature detected value T by the oil temperature detector 12 and a value of the capacitance C _X obtained by the first calculating unit 13b. The value of the ratio α between the DC insulation resistance value R _DC and the AC insulation resistance value R _AC is read from the memory 13a, and the AC insulation resistance value R _AC obtained by the first arithmetic unit 13b from the value of the ratio α is read.
To a DC insulation resistance value R _DC , and obtains a DC insulation resistance value R _DC . Note that FIG.
, The arrow indicated by a dotted line from the second operation unit 13c to the memory 13a indicates the memory 1 by the second operation unit 13c.
3a, and the first arithmetic unit 13b calculates the dielectric loss tangent tan δ in addition to the _AC insulation resistance value R _AC and the capacitance C _X. Is the AC insulation resistance value R _AC
The capacitance C _X and the dielectric loss tangent tan δ can also be output in addition to the DC insulation resistance value R _DC and the DC insulation resistance value R _DC , and are used for comprehensive evaluation of insulation diagnosis.

FIG. 3 shows, for example, a rated voltage of 6.6 KV-
It describes the contents stored in the memory 13a in which the value of the ratio α of the DC insulation resistance value R _DC and the AC insulation resistance value R _{AC to} the oil temperature of the oil-immersed transformer 2A of less than 22 KV is stored in advance.
With the capacitance Cx as a parameter and the oil temperature T of the oil-immersed transformer 2A on the horizontal axis, the ratio α between the DC insulation resistance R _DC and the AC insulation resistance R _AC of the oil-immersed transformer 2A is expressed on the vertical axis. This enables AC-DC conversion of the indicated AC value and DC value of the insulation resistance. For example, if the AC insulation resistance R _AC obtained by the oil-immersed transformer 2A at an oil temperature T of 40 ° C. is 100 MΩ and the simultaneously obtained capacitance C _X is 2 nF, α = 15 should be adopted. Thus, the DC insulation resistance R _DC can be estimated to be 1500 MΩ.

In FIG. 3, five solid lines (corresponding to Cx = 1, 2, 3, 5, 10 nF) of the capacitance Cx as a parameter are the DC insulation resistance conventionally used and shown in FIG. The allowable value curve of R _{DC and} the dielectric loss tangent tan shown in FIG.
It is derived by the following procedure based on the criterion of δ. Now, if the insulation state of the oil-immersed transformer is represented by a parallel equivalent circuit of the capacitance Cx and the insulation resistance Rx, the AC dielectric loss tangent t
anδ is given by the following equation. tan δ = 1 / (2πfCxRx) (1) where f is the frequency of AC power application. If the insulation resistance Rx in the equation (1) is replaced by the AC insulation resistance R _AC , R _AC = 1 / (2πfCxtan δ) (2)
From the nδ value, the allowable value of the _AC insulation resistance R _AC corresponding to various capacitances Cx can be calculated from the equation (2). On the other hand, since the allowable value of the DC insulation resistance R _DC is given in FIG. 4, for example, in an oil-filled transformer having a rated voltage of 6.6 KV to less than 22 KV, α = R _DC / R _AC as shown in FIG. An oil temperature conversion curve is derived.

In the conversion diagram shown in FIG. 3, markings A to D indicate the ratio α of the DC insulation resistance R _DC and the AC insulation resistance R _AC actually measured for several types of operating high-voltage transformers to the capacitance Cx. (3φ200 KVA indicates a rated capacity of 200 KVA in a three-phase transformer). From these results, the conversion diagram of the _AC insulation resistance R _AC and the DC insulation resistance R _DC derived by the present invention shows that It has been verified that the effect that the AC insulation resistance R _AC obtained by the oil-immersed transformer as the power failure insulation diagnosis device can be converted to the DC insulation resistance R _DC with good accuracy can be obtained.

That is, in the insulation diagnosis apparatus for an oil-immersed transformer shown in FIG. 1, when a clamp-type transformer 5 magnetically coupled to the ground wire 4 of the oil-immersed transformer 2A as a device to be diagnosed is excited by a high-frequency power supply 6, , A high-frequency voltage V _S is induced at the point a of the ground line 4, and the leakage current Ix flows to the power supply side via the drop cable 9 via the insulation resistance Rx and the capacitance Cx of the oil-immersed transformer 2A. This can be detected by the current sensor 10 which is collectively clamped to the lead-in cable 9.

The measuring unit 13 which inputs the high-frequency voltage V _S and the leakage current _IX converts the AC insulation resistance R _AC of the oil-immersed transformer 2A into the DC insulation resistance R _DC with good accuracy as follows. . First, the first calculation unit 13b performs an operation on the oil-filled transformer 2 based on the detection values of the high-frequency voltage V _S and the leakage current Ix.
A AC insulation resistance value R _AC and capacitance Cx of A are obtained,
A second calculating unit 13 for inputting the oil temperature detection value by the oil temperature detector 12 together with the _AC insulation resistance value R _AC and the capacitance Cx.
c, the value of the ratio α between the DC insulation resistance value R _DC and the AC insulation resistance value R _AC corresponding to the oil temperature detection value and the value of the capacitance C _X is read from the memory 13a, and The DC insulation resistance value R _DC is obtained by converting the _AC insulation resistance value R _AC obtained by the first calculation unit 13b into a DC insulation resistance value R _DC . In this manner, the outputs of the measuring unit 13 include, besides the _AC insulation resistance value R _AC and the DC insulation resistance value R _DC , the capacitance C _X and the dielectric constant C _X simultaneously obtained by the first calculation unit 13b. The tangent tan δ can also be output and used for comprehensive evaluation of insulation diagnosis.

As described above, according to the first embodiment,
By energizing a clamp-type transformer 5 magnetically coupled to the ground line 4 of the oil-immersed transformer 2A with a high-frequency power source 6, the high-frequency voltage induced on the ground line 4 and the oil-immersed transformer 2A are excited.
In the insulation diagnosis device for an oil-filled transformer provided with a measuring unit 13 which detects a leakage current flowing out to the power supply side via the measuring unit 13 and performs an insulation diagnosis of the oil-filled transformer 2A based on the detected values,
An oil temperature detector 12 for detecting the oil temperature of the oil-immersed transformer 2A is provided, and the measuring unit 13 is a ratio of a DC insulation resistance value to an AC insulation resistance value with respect to the oil temperature of the oil-immersed transformer 2A. And a first calculating unit 13 for obtaining the AC insulation resistance value and the capacitance of the oil-filled transformer 2A based on the detected values of the high-frequency voltage and the leakage current.
b, and the value of the ratio between the DC insulation resistance value and the AC insulation resistance value according to the oil temperature detection value obtained by the oil temperature detector 12 and the capacitance value obtained by the first calculation unit 13b. 13a, and converts the AC insulation resistance value obtained by the first calculation unit 13b into a DC insulation resistance value from the ratio value to obtain a DC insulation resistance value.
3c, the AC insulation resistance obtained by the insulation diagnosis under non-power failure can be converted to DC insulation resistance, and DC insulation resistance under non-power failure can also be obtained. Resistance trend management can be performed.

Embodiment 2 FIG. In the first embodiment described above, α for the oil-filled transformer having a rated voltage of 6.6 KV to less than 22 KV
Although the derivation of the conversion of = R _AC / R _DC has been described, as shown in FIG. 4, the oil-immersed transformer having the other three rated voltages can be similarly derived, and the same effect can be obtained.

[0018]

As described above, according to the present invention, the ratio of the DC insulation resistance value to the AC insulation resistance value with respect to the oil temperature of the oil-immersed transformer is previously stored in the memory in the measuring unit, The oil temperature of the oil-immersed transformer is detected by the detector, and the AC insulation resistance and the capacitance of the oil-immersed transformer are detected by the first arithmetic unit in the measuring unit based on the detected values of the high-frequency voltage and the leakage current. And a ratio of a DC insulation resistance value to an AC insulation resistance value corresponding to the oil temperature detection value obtained by the oil temperature detector and the capacitance value obtained by the first calculation unit is calculated by the second calculation unit. Is read out from the memory, and the DC insulation resistance value obtained by converting the AC insulation resistance value obtained by the first arithmetic unit into the DC insulation resistance value from the value of the ratio is obtained. Conversion of AC insulation resistance obtained by insulation diagnosis to DC insulation resistance Te, can be obtained a direct current insulation resistance under non power failure, there is an effect that, without the outage constraint may perform trend management of the insulation resistance.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an insulation diagnosis device for an oil-immersed transformer according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a measurement unit of FIG. 1;

FIG. 3 is an explanatory diagram of contents stored in a memory of FIG. 1;

FIG. 4 is a diagram for deriving a ratio of oil temperature to DC insulation resistance and AC insulation resistance shown in FIG. 3, and is an explanatory diagram of a conventionally used allowable value curve of DC insulation resistance.

5 is a diagram for deriving a ratio of oil temperature to DC insulation resistance and AC insulation resistance shown in FIG. 3, and is an explanatory diagram of a criterion for determining a dielectric loss tangent.

FIG. 6 is a configuration diagram illustrating a conventional non-power failure insulation diagnosis device for electric equipment.

7 is a vector diagram of a high frequency voltage V _S and the leakage current I _X.

[Explanation of symbols]

2A oil-filled transformer, 4 ground wire, 5 clamp type transformer, 6 high frequency power supply, 10 current sensor, 12 oil temperature detector, 13 measuring unit, 13a memory, 13b first calculating unit, 13c second calculating unit .

Claims (1)

(57) [Claims] 1. A transformer magnetically coupled to a ground line of an oil-immersed transformer as a device to be diagnosed is excited by a high-frequency power supply to pass a high-frequency voltage induced on the ground line and the oil-immersed transformer. In the insulation diagnosis device of the oil-filled transformer having a measuring unit that detects the leakage current flowing out to the power supply side and performs an insulation diagnosis of the oil-filled transformer based on the detected values,
An oil temperature detector for detecting the oil temperature of the oil-immersed transformer is provided, and as the measuring unit, a value of a ratio of a DC insulation resistance value and an AC insulation resistance value to the oil temperature of the oil-immersed transformer is stored in advance. A first calculating unit for obtaining an AC insulation resistance value and a capacitance of an oil-immersed transformer based on the detected values of the high-frequency voltage and the leakage current; and a detected oil temperature value by the oil temperature detector. And reading a value of a ratio between a DC insulation resistance value and an AC insulation resistance value according to the value of the capacitance obtained by the first calculation unit from the memory, and from the ratio value by the first calculation unit. A second calculating unit for converting the obtained AC insulation resistance value into a DC insulation resistance value to obtain a DC insulation resistance value.