JPS598129B2 - OF cable oil leakage monitoring method - Google Patents

Description

[Detailed Description of the Invention] This invention determines the average temperature of the OF cable from the conductor resistance value of the electric wire attached to the cable line, estimates the amount of oil in the oil tank, and compares it with the actually measured oil amount in the oil tank. It relates to a method for monitoring oil leaks.

Conventionally, monitoring for oil leakage from OF cables only involves checking that the oil level in the oil tank is between the upper and lower limits, and the oil level changes greatly due to seasonal temperature changes and load fluctuations, resulting in a total change in oil volume. It is difficult to detect oil leaks early on cable lines by monitoring upper and lower limit values.

For this reason, constant measurement and monitoring of the oil volume in the oil tank is performed centrally, and cable temperature, load current, oil tank temperature, oil tank gas pressure,
Efforts have been made to detect oil leaks early by calculating the theoretical oil amount by understanding the condition of OF cable lines such as the above, and comparing it with the actual oil amount.

In the above-described oil repellent monitoring method, it is necessary to accurately know the average temperature of the entire OF cable.

There are two ways to find out the temperature of the OF cable, such as inserting a lead wire into the OF cable junction box and connecting a temperature sensor such as a thermistor to the end of the lead wire, and attaching a thermocouple to the surface of the OF cable. Although these methods have been proposed, the temperature of a limited portion of the OF cable is measured, and if these temperatures are used as a reference, the estimation of the oil amount may become uncertain.

In addition, as a method of knowing the average temperature of an OF cable, a method has been proposed in which a resistance wire is buried in the OF cable and the temperature is determined from the change in resistance.

Burying a resistance wire in an OF cable is undesirable and impractical due to the characteristics of the cable and from the viewpoint of manufacturing.

This invention was made against the above background, and it measures the DC conductor resistance of the electric wire attached to the cable line, converts the temperature from the change in this resistance value, and calculates -C, load current, It is an object of the present invention to provide a method of estimating the amount of oil in an oil tank from oil tank temperature, oil tank gas pressure, etc., and comparing it with the actually measured oil amount in the oil tank to monitor oil leakage from an OF cable.

The present invention will be explained in detail below.

As shown in Fig. 1, a reciprocating electric wire (twisted pair wire or coaxial wire) 2 whose DC conductor resistance r1 has been determined in advance at a measurement temperature T1 is laid parallel to the line of the OF cable 1, and this electric wire 2 By short-circuiting one end and connecting the other end to the resistance meter 3, the DC conductor resistance value r2 is determined. If the electric wire 2 is a copper wire, the average temperature T2 of the electric wire 2 can be calculated by the following formula.

Along with the average temperature T2 calculated from the above formula depending on the state of the electric wire 2, the load current taken out by the current transformer 4, the temperature of the oil tank 5, and the gas pressure are input into an arithmetic circuit (computer). The OF calculates the theoretical value of the oil amount in the oil tank and compares the result with the actual oil amount sent from a portable oil amount monitoring device 6 that can be detachably connected to an oil tank to detect the presence or absence of oil leakage. A cable oil leakage monitoring method, particularly the method of the present invention, is that a conductor resistance measuring wire 2 is attached to the OF cable.

The portable oil level monitoring device 6 is, for example, one that converts minute oil pressure at the lower end of an oil tank oil level gauge into an electrical signal and transmits it, or an oil level detection device and an oil level detection device equipped on a rotary wheel that rotates when the floating body moves up and down. It is equipped with an oil level transmitting device that is driven by the driving wheels and extracts the rotation angle of the rotating wheels as a change in voltage.

FIG. 2 shows an embodiment in which conductor resistance measuring wires, which constitute the main component of the present invention, are installed together, and a large number of conduits 7
is constituted by a concrete wall 8 as an example.

OF cables 1 are laid through these several conduits 7, and resistance measuring wires 2 are arranged in the empty conduits.

On the other hand, FIG. 3 shows another embodiment in which a resistance measuring wire 2 is placed along the surface of an OF cable 1 installed in a trough 12 supported by a hanger 11 provided in an underground tunnel 10. This is the wiring that was done.

Note that the DC conductor resistance measurement of the electric wire 2 is possible in both the loaded and unloaded OF cable 1 conditions.
In order to avoid induction interference from the OF cable 1, etc., a twisted pair wire with a shielding layer or a coaxial wire is preferable.

In the embodiment shown in Fig. 2, the conductor resistance measuring wire is
Since it is far from the F cable 1, the average temperature around the OF cable track must be measured, but if a conversion formula determined by the surrounding conditions is set in the computer in advance, the average temperature of the OF cable can be easily determined.

Furthermore, depending on the installation location of the oil tank, it is also possible to use this resistance measurement wire to send oil level signals and oil tank temperature signals to the computer.

As described above, the oil leak monitoring method of the present invention calculates the estimated oil amount from the OF cable line surrounding temperature, load current, oil tank temperature, oil tank gas pressure, etc., compares it with the actual oil amount, and detects an oil leak based on the difference. Because of this, its accuracy is very high and even minute oil leaks can be easily detected.

Furthermore, since the conductor resistance measuring wire only needs to be laid in an empty conduit or in a trough, there is an advantage that it can also be used for existing OF cables.

[Brief explanation of drawings]

Fig. 1 is a conceptual explanatory diagram of the present invention, Fig. 2 is a cross-sectional view showing the installation state of a conductor resistance measuring wire in an embodiment to which the invention is applied, and Fig. 3 is another embodiment to which the invention is applied. FIG. 1...OF cable, 2...Conductor resistance measurement wire, 3
... Resistance meter, 5... Oil tank, 6... Portable oil amount monitoring device, 7... Cable conduit, 12... Cable trough.

Claims (1)

[Claims] 1. The DC conductor resistance of the electric wire attached to the 0F cable line, the OF cable load current, the oil tank temperature, the oil tank gas pressure, etc. are input into an arithmetic circuit to estimate the amount of oil in the oil tank. An OF cable oil leak monitoring method characterized in that an oil leak is detected by comparing an estimated oil amount with an actually measured oil amount in an oil tank. 2. The OF cable oil leakage monitoring method according to claim 1, wherein the amount of oil is estimated by measuring the DC conductor resistance of the electric wire installed in the empty conduit of the cable installation conduit. 3. Claim 1, which estimates the amount of oil by measuring the DC conductor resistance of the electric wire laid in the trough in which the cable is laid.
OF cable oil leakage monitoring method described in section.