JPS592866B2 - Hengatsukinountenjiyoutaiohiyoujishijiyumiyouoyosokusultamenosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Y/Y0=e-0.1155(θH- In equation (1), (θHo) is the reference winding temperature determined by the type of insulation of the transformer.

As shown in FIG. 1, the life span decreases exponentially depending on the temperature, and the life span is halved for every 6° C. rise.

The relationship between this winding temperature and load is as shown in the formula (2) (3)
It is given by equation (4).

θH■θa+θo+θg ・・・・・・・・・・・・(
2) The present invention relates to a device for predicting the tendency of the life of oil-immersed power transformers installed in power distribution stations, substations, etc. against overload.

In general, it is well known that the lifespan of a transformer will be significantly reduced if it is overloaded, and that its operating efficiency will deteriorate if it is lightly loaded, but power transformers require a huge amount of equipment cost. Therefore, if the transformer can be operated efficiently while maintaining its normal service life, it will have a large economic effect.

The present invention has been made with this point in mind. The lifespan of a transformer is most likely to be affected not by the magnitude of the load itself, but by how the deterioration of the transformer insulation progresses due to the load.

This is mainly closely related to the transformer winding temperature. That is,
The relationship between winding temperature (θH) and life allowance is normal life (Yo)
is expressed as the following equation (1) using Montsinger's equation.

Ho)■ 2-(θH-θHo)/6 ・・・・・・
・・・・・・・・・・・・(1) θo: Temperature rise in oil temperature relative to ambient temperature, θ ゜ Temperature rise in winding temperature relative to ambient temperature, and g' Oil temperature relative to ambient temperature. Since the winding temperature (θH) indicates the absolute temperature, it is necessary to add the ambient temperature (θa).

2R+1mθo■θoN(-)・・・・・・・・・(
3) R+1θ, -θ8N(K)2n・・・・・・・・・
・・・・・・・・・・・・・・・(4) Here, θ0N
; Temperature rise in oil temperature relative to ambient temperature at rated load, θ
GN: difference between winding temperature and oil temperature with respect to ambient temperature at rated load, K, ratio of actual load to rated load, R, ratio of load loss to no-load loss at rated load, m and N, cooling Constant determined by method.

FIG. 2 illustrates the relationship expressed by equation (2), and the ambient temperature has been omitted since it can be ignored.

The conventional method for predicting the lifespan of a transformer is to use a platinum resistance thermometer to measure the oil temperature (θo) and a load ammeter to measure the magnitude of the load, which are equipped to monitor the operation of the transformer. The lifespan was predicted by estimating the winding temperature (θH) based on experience.

It is clear from the above description that this method is easy to predict for a constant load that does not fluctuate, but is inaccurate for a load that fluctuates a lot. The present invention has been made in view of this point, and makes it possible to reasonably predict the lifespan.

The present invention will be explained in detail below. The life prediction method according to the present invention calculates the time when the normal life (life when used within the reference winding temperature θHO determined by the type of insulation of the transformer) is reached by shortening Vc by a certain period (t), and during this period, The case of operation at the reference winding temperature (θHO) is defined as 100%.

Therefore, when the load is light, the winding temperature (θH) is low and 100%.
The time it takes to reach 100% is longer than t, and conversely, when there is an overload, (θH) increases and the time it takes to reach 100% becomes shorter, so if you continue to operate in this condition, the life will be shortened. suggest. In this device, the winding temperature, which is closely related to the life of the transformer, is converted into a voltage, and this voltage is used to charge a potential storage element, which will be described later. That is, the amount of charged air accumulated in the potential storage element is the product of the current proportional to the voltage corresponding to the winding temperature and the operating time of the transformer.

The potential storage element has a characteristic that its potential changes approximately linearly depending on the amount of charged air. If a display circuit operated by the potential of the potential storage element is provided, the purpose of predicting the life of the transformer can be achieved more accurately and easily. Next, an embodiment of the apparatus of the present invention will be explained in more detail with reference to a specific electric circuit diagram shown in FIG.

The device of the present invention detects the oil temperature (θo) using a platinum resistor TH in the line where power is transmitted and distributed from the power supply S to the load L via the transformer T, and the temperature difference (θ ) between the winding and the oil temperature is From the relationship of equation (4), the secondary current of the load current measuring current transformer GCTl is further detected by the auxiliary current transformer CT2.

Input converter A for converting these as input signals,
A level detection amplification section B detects and amplifies the signal from A to a level required for integration, an exponential function amplification section C follows the life curve of the above equation (1), and the output from this exponential function amplification section C is set to a potential. It is composed of an integration display section D that integrates in the memory element MD and displays potential changes of this element MD, and a measurement period setting section G that includes a repeat timer that determines the measurement period.

Note that the potential storage element MD has a solid electrolyte E having high ionic conductivity sandwiched between a cathode N and an auxiliary cathode N/ for potential detection, which are mainly made of silver, and an anode P, which is mainly made of silver chalcogenide. In this type of battery, when electricity is applied from the anode P to the cathode N (this is called charging), the silver in the silver chalcogenide at the anode P becomes ions and is deposited on the cathode N via the solid electrolyte E, and Conversely, when electricity is applied from the cathode N to the anode P (this is called discharge), the deposited metal is redeposited on the anode P.

The potential of this element is detected between the anode P and the auxiliary cathode N',
It has a characteristic that changes approximately linearly depending on the amount of current applied. Now, the input converter A passes current from the power supply (E1) through the resistor R1 to the platinum resistor TH, and uses the voltage drop across the platinum resistor TH as a signal of the oil temperature (θo), and adds it to the auxiliary current transformer. The output voltage of the device CT2 is connected to the diodes D1 to D4.
It is rectified by , smoothed by capacitor C1, and is used as a signal of the temperature difference (θ) between the winding and the oil temperature.

However, (θ) is a coefficient (substitute) of 0 as shown in equation (4) above.
g, and the output of the auxiliary current transformer CT2 is proportional to the coefficient.

Therefore, since the output of CT2 itself has many errors, a conversion circuit is required. It would be more accurate if an exponential amplification circuit was used for this conversion circuit, but since the range of coefficients (substitutes) is limited to some extent, the ideal characteristic 1 as shown in Figure 3.
However, even if the conversion is performed using a straight line 2 that approximates the necessary K range K1 to K2, it will not cause much trouble.

This example is a method using an approximate straight line, and on straight line 2 (KO
), the smoothed output of the auxiliary current transformer CT2 is adjusted to match the output voltage per unit temperature of (θo) so that (θ, ) becomes zero, and then the resistors R4 and R5 are adjusted.
and (-E2) are subtracted by the power supply. Next, the level detection amplifying section B receives θ from the input converting section A.

A signal of +θ8−θH is input. This input is used to amplify the voltage corresponding to the reference winding temperature (θHO) or higher (+E
2) The power supply is divided by resistors R7 and R8, and the resistors R, l,
R,3 to the non-inverting input of the amplifier 0P1, and (
A signal of θH) is input to the inverting input via the resistor Rl2.
In addition, since the voltage corresponding to the temperature below the reference winding temperature (θHO) is not integrated, a comparator circuit consisting of an amplifier 0P2 is provided, and the voltage of the resistor R8 is passed through the amplifier 0P2 through the resistor R6.
Since the voltage corresponding to the winding temperature (θH) is input to the non-inverting input of P2 via the resistor Rl5, the voltage corresponding to the winding temperature (θH) is the voltage of the resistor R8 (reference winding temperature (corresponding to the voltage), a positive step voltage is generated at the output of amplifier 0P2, transistor Q1 is turned ON, relay LA is energized, and its contact a1 is closed to form a charging circuit for potential storage element MD.

Furthermore, in view of equation (1), when the voltage M applied to the potential storage element MD is converted to the normal lifetime voltage (VO), the following equation is obtained.

v-VO×2(θH-θHO)/6 ・・・・・・(5
) In equation (5), for example, when the reference winding temperature (θHO) is 95°C, and when the winding temperature (θH) is 95°C and the applied voltage M is 0.1V, (θH) is 1'55 At ℃ (
(b) requires 102.4V, which far exceeds the operating voltage of the amplifier.

Therefore, it is necessary to switch the input range at the winding temperature (θH1) corresponding to the upper limit of the voltage at which the amplifier can operate. This situation is shown in FIG.

In other words, for the required characteristic curve 1, up to the winding temperature (θH1), which corresponds to the upper limit of the amplifier's operable voltage, curve 1
and above (θH1), curve 2 starts again from (VO). At this time, since the amount of charge in the potential storage element MD decreases, it is natural to switch the charging resistance to reduce it by the amount that the applied voltage (b) has decreased.

An amplifier 0P3 is provided to switch the charging resistance, and a potential corresponding to (θH1) is generated by the resistors R, , RlO and input to the non-inverting input of the amplifier 0P3 via the resistor Rl8. A potential corresponding to (θH) is input to the inverting input via R, 7, and when the potential of (θH) exceeds the potential of (θH1), the output of amplifier 0P3 generates a positive step voltage, which is applied to the next stage. transistor Q2 becomes 0N, relay L
B is excited. As a result, the first contact b1 of the relay LB is closed, so that the (+E2) power is supplied to the resistor R via the resistor R6.
ll, and the non-inverting input of amplifier 0P1 is connected to resistor R8.
The voltage is the sum of the voltage of the resistor Rll and the voltage of the resistor Rll (θH,
) can be switched to an amplification level higher than the voltage corresponding to the voltage.

At the same time, the second contact B2 of the relay LB closes, and the charging resistance of the potential storage element MD changes from only the resistor R35 to the resistor R.
35 and R36 are connected in parallel and decrease.

Exponential function amplification section C connects the output from level detection amplification section B to resistors R2l, R22, power supply (+E2) and resistors R23, R.
24 to the required input voltage and then applied to the base of transistor Q3. Then, the level is shifted to the voltage between the base and emitter of the transistor Q4 using the transistor Q3 and the amplifier 0P4. Since this voltage changes depending on the base voltage of transistor Q3,
4 changes exponentially, and as a result, the output voltage of amplifier 0P5 changes exponentially due to the collector current flowing through resistor R29. In other words, the winding temperature (θH) and life 7 shown in equation (1) are determined by this exponential function amplification part C.
Satisfied with the relationship. Incidentally, since the polarity of the output voltage of the amplifier 0P5 is positive, the polarity is reversed by the amplifier 0P6 to make it a negative polarity voltage that is easy to charge the potential storage element MD, and then the exponential function amplifier Let it be the output of C.

In the integration display section D, the contact a1 of the relay LA and the charging resistor R35 or R36 are excited depending on the integration level.
The potential storage element MD is charged through the amplifier 0P7, and the output voltage of the element MD, which changes according to the charging capacity, is amplified by the amplifier 0P7, and the potential is continuously displayed on the display meter M. When the aforementioned 100% integral amount (the amount when operating for a predetermined time at the reference winding temperature) is reached, the amplifier 0 that constitutes the comparison circuit is activated.
P8 generates a positive step voltage because the voltage applied to its non-inverting input, that is, the voltage obtained by dividing the power supply (-E2) by resistors R43 and R44, matches the voltage at its inverting input.
As soon as the transistor Q5 becomes 0N, the transistor Q,
The alarm light emitting diode D5 connected to the collector lights up.

The repeat timer G is used to set a measurement period, and after a predetermined measurement period has elapsed, the timer contact g closes and the integrated charge of the potential storage element MD is forcibly discharged from the power supply (-E2) via the discharge resistor R37.

When the integrated amount becomes zero, the output of the amplifier 0P7 also becomes zero, and the inverting input of the amplifier 0P9 forming the comparison circuit becomes zero, so it matches the zero of the non-inverting input, and the output becomes a positive voltage and the transistor Q6 becomes 0N, and relay Lc is also excited. As a result, contact C1 of relay Lc opens and potential storage element MD
discharge stops. After the end of this discharge, the contact g of the timer G is opened again after the measurement stop period has elapsed to perform so-called automatic repeat measurement in preparation for the next measurement. To explain the above operation using the characteristic diagram in Figure 5, in the first measurement A, the winding temperature (θH) is maintained at the reference winding temperature (θHO), and the measurement period (t) (solid line The integration amount becomes 100% at the end of the measurement period (t), and the potential E of the potential storage element MD becomes 100% at the end of the measurement period (t). Predetermined value (
EO), suggesting ideal operating conditions. Next, prepare for the second measurement after the discharge time (t), that is, the dust is set. This is when the winding temperature (θH) at the end of the second measurement is higher than the reference winding temperature (θHO), and the potential storage element MD The time (T2) until the potential of reaches the predetermined value (EO) is the first
It is earlier than the second time (t1). Moreover, the third measurement C shows a case where the winding temperature (θH) is even higher. As described above, the device of the present invention converts the winding temperature, which is closely related to the life of the transformer, into voltage by focusing on the fact that the winding temperature changes functionally due to changes in oil temperature and load. Furthermore, this voltage is converted into an index based on the exponential relationship between the winding temperature and the life of the transformer, and this voltage is used to charge the potential storage element and continuously display changes in the element potential. The system compares the winding temperature during ideal operation x amount of operating time and issues an alarm when there is an overload condition.By checking the integrated value through regular inspections, it is possible to easily predict the lifespan. If there is a load condition that shortens the life of the transformer, connect the load to another transformer and switch to an appropriate load.
If the load is light and does not affect the service life, rational operation can be carried out by switching the load to another and stopping the equipment.

[Brief explanation of the drawings] Fig. 1 is a characteristic diagram showing the winding temperature versus life, Fig. 2 is a characteristic diagram showing load factor versus temperature, and Fig. 3 is a characteristic diagram showing the temperature difference between the winding and oil versus load factor. FIG. 4 is a characteristic diagram showing the winding temperature versus output voltage, FIG. 5 is a characteristic diagram showing the winding temperature and potential storage element voltage change with respect to operating time, and FIG. 6 is a characteristic diagram showing the winding temperature versus output voltage. FIG. 2 is an electrical circuit diagram of one embodiment. T...Transformer, A...--Input converter, B
...Level detection unit, C...Exponential function conversion section, D...Display section, G...Repetition neumar, S... Power supply, L...Load, C
Tl...Main current transformer, CT2...Auxiliary current transformer, TH...Platinum resistor, D1-D4...
... Rectifying diode, 0P1 to 0P9 ... Amplifier, MD ... Potential storage element, D5 ...
・Light-emitting diode, M...Display meter, LA-LO
...Relay, Q1-Q6...Transistor, C1...Smoothing capacitor, R1-R49
······resistance.

Claims (1)

[Claims] 1 A first detection circuit that detects the oil temperature of the transformer and converts it into voltage; a second detection circuit that detects the load current of the transformer; A conversion circuit that converts into a voltage corresponding to the difference, a level detection circuit that operates only when the sum of these detected voltages exceeds a predetermined value, and an exponential function circuit that converts the summed voltage into a voltage that corresponds to the life of the transformer. and a potential storage element whose charging/discharging time is regulated by a repeat timer and which is charged by the output of the exponential function circuit and whose potential changes approximately linearly according to the amount of current supplied thereto, and a potential change of the element. A device for displaying the operating status of a transformer and predicting its lifespan, which is equipped with a display circuit that responds to the current state of the transformer.