JP3010499B2 - Oil leak detection system for OF cable line - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil leak detection system for an OF cable line, and more particularly to a system suitable for detecting a large oil leak.

[Conventional technology]

Conventionally, in order to detect oil leaks in OF cable lines, a method was used in which an oil amount alarm transmitter was used, and an alarm was automatically issued when it detected that the oil amount had dropped below a specified value. .

However, according to this method, the alarm is notified only when the oil level drops to the alarm set point, so not only the oil leak detection timing is delayed, but also an alarm may be generated regardless of night or holiday. In addition, particularly in summer, there is a problem that the amount of outflow until receiving the warning is large.

In order to eliminate such problems, a method for detecting oil leakage has been proposed by comparing the change pattern of the measured oil amount under the same conditions in the past on the OF cable line with the change pattern of the actual oil amount. (JP-A-2-28529).

However, it is difficult for the above method to accurately select data under the same conditions in the past, and even if a pattern changes, it is impossible to determine the occurrence of oil leakage unless a change over a certain period is observed. There's a problem.

Therefore, the present invention utilizes the characteristic of the change in the oil amount in the oil tank over time when the load current of the OF cable line changes (so-called transient state), thereby making it possible to quickly determine the presence or absence of oil leakage. The purpose is to provide a system.

[Means for solving the problem]

In order to solve the above-mentioned problem, the present invention has an oil amount sensor that detects an oil amount in an oil tank, and a determination unit that determines the presence or absence of oil leakage based on oil amount data detected by the oil amount sensor. In the oil leak detection system of the OF cable line having the above, the determination means may occur due to a temporal change in the oil amount decrease speed of the actually detected oil tank and a change in the load current due to the load change. The configuration is such that the presence or absence of oil leakage is determined by comparing the oil amount change characteristic.

 The details will be described below.

Generally, when oil leaks in the OF cable line, the amount of oil in the oil sump decreases,
For example, it fluctuates due to load fluctuation, temperature change, and the like. For this reason, even if the tendency to decrease the amount of oil in the oil tank is detected,
It is difficult to quickly determine if it is due to an oil leak.

However, the inventor of the present application has conceived of determining the presence or absence of oil leakage based on the following idea.

That is, the example of the oil demand at the time of load rejection is the first oil demand.
A (t) = a · e- ^mt (1) where, a (t): oil demand t seconds after load shedding a: oil demand just after load shedding It is well known that m can be approximated by the reciprocal of the oil demand time constant.

The oil demand refers to the amount of oil change per unit length of cable and unit time.

From the above equation (1), the change oil amount Vt after t seconds after the load rejection is obtained.
Is However, at t = 0, it is represented by Vt = 0.

Here, t = 0, t = t ₁ , t = t ₂ (= 2t ₁ ), and t
= T ₃ Vt ₀ change oil amount V _t in _{(= 3t 1), Vt 1} , Vt 2 and
Assuming Vt ₃ , as shown in FIG. Becomes

The change amount ΔV ₁ of the oil amount at each of the above times t ₁ , t ₂ , t ₃ ,
ΔV ₂ and ΔV ₃ are as follows.

Here, the reduction ratio of the oil amount as well as And ask for Is established. Here, ΔV ₁ ≠ ΔV ₂ ≠ ΔV ₃ .

Although the above is the phenomenon at the time of load interruption, the transient change of the oil amount due to the rapid decrease of the load shows the same tendency, although there is a difference in the oil demand, and the relationship of the equation (5) is established. I do.

On the other hand, if the oil leak rate does not change, the oil amount change due to the oil leak accident
It is proportional to time as shown in FIG. Accordingly, since the oil amount reduction ratio in this case is ΔV ₁ = ΔV ₂ = ΔV ₃ , Is a special condition.

Since the oil amount change at the time of load rejection and oil leakage is as described above, if both changes occur at the same time, the oil amount change is superimposed, as shown in FIG. ΔV _{1 in} this case
≠ ΔV ₂ ≠ ΔV ₃ is the same as in the transient state without oil leakage, but the oil amount reduction ratio is Which is different from the expression (5).

That is, the change oil amount due to the transient phenomenon is represented by ΔV ₁ ′, ΔV ₂ ′, Δ
V ₃ ′ and the amount of oil leakage ΔL After all, on the other hand, Because Becomes

As described above, the oil amount reduction ratio associated with the load fluctuation when the line is sound is in the relationship shown in Expression (5), and when oil leakage is superimposed on this, there is the relationship in Expression (7).

Therefore, in the initial stage of the transition due to load fluctuation, e
^-mt1 is the reference for comparison, The presence or absence of oil leakage can be determined by comparing After that, Is the reference for comparison, The presence or absence of oil leakage can be determined by comparing

In any case, it is desirable to give a certain judgment allowance to the above judgment criteria in order to prevent the occurrence of a false alarm in consideration of the measurement accuracy and the variation in the actual line.

The above Are general formulas, as well as Can be shown.

〔Example〕

FIG. 5 is a configuration diagram of the system, including an oil tank 1, a control station 2, and a power station 3. The oil tank 1 has an oil tank 4, a terminal device 5, a telephone line switching device 6, and the like. The output of the oil amount sensor 7 provided in the oil tank 4 is input to the terminal device 5. When detecting the occurrence of a large oil leak based on the input oil amount data, the terminal device 5 transmits a large oil leak alarm to the control station 2,
It is displayed on the monitoring panel 8. The oil amount data is transmitted to the master station 11 via the telephone line switching device 6, the telephone line 9, the power station 3, and the telephone line switching device 10.

FIG. 6 shows the internal structure of the terminal device 5. The detection signal detected by the oil amount sensor 7 of the oil tank 1 is passed through the controller 12 to the current / voltage converter 13 of the terminal device 5 and the multiplexer. 14. It is taken into the bus 16 via the A / D converter 15. The ROM 17 stores programs for data input, large oil leak determination, communication, and the like. The RAM 18 accumulates oil amount data for a certain period of time, such as for one day or every hour. The CPU 19 performs a series of processes based on a predetermined program.

On the other hand, a no-voltage alarm contact converter 21 is connected via a PIO interface 20, and a large oil leak signal is transmitted to the control station 2 through this device 21. The telephone line switching device 6 is connected via the SIO interface 22, and transmits oil quantity data to the master station 3 through the device 6.

FIG. 7 is a flowchart showing a process of determining a large oil leak by the CPU 19 of the terminal device, and comprises the following steps.

Step: Acquire oil amount data at fixed time intervals, for example, every 0.1 hour. Step: Determine whether the oil amount is decreasing or not by comparing with the immediately preceding data.

Step: If there is a decreasing tendency, the oil amount difference ΔV ₁ between the time and the time t is measured.

Steps: Is calculated and compared with the expected detection value ΔLe.

Step: If the detected expected oil amount ΔLe is exceeded,
Next, the reduced oil amount ΔV ₂ at the time t is measured.

Steps: Is calculated and again compared with the expected detection value ΔLe.

Step: If the detected value exceeds the expected value ΔLe, the oil amount decrease ratio And compare it with e- ^mt1 · α. e ^-mt1 · α is a determination criterion, and α is a determination ^allowance .

Step: Send an alarm signal.

Step: Step-by-step oil reduction ratio If does not exceed the determination criterion, the reduced oil amount ΔV ₃ within the next t time is further measured.

Steps: Is calculated and compared with the expected detection value ΔLe.

Step: When the detected value exceeds the expected value ΔLe, the oil amount reduction ratio based on the previously measured ΔV ₁ and ΔV ₂ And the oil amount reduction ratio due to ΔV ₂ and ΔV ₃ And a judgment criterion obtained by multiplying the result by a reciprocal of a predetermined judgment allowance β.

If is smaller than the criterion, the process proceeds to step and an alarm is sent out.

If the determination in step is negative, the process returns to step.

〔The invention's effect〕

As described above, the present invention compares the temporal change of the oil amount decrease speed of the actually detected oil tank with the oil amount change characteristic that can be caused by the change of the load current due to the load change. Is used to determine the presence or absence of a large oil leak, so that there is an effect that a large oil leak can be detected early.

[Brief description of the drawings]

FIG. 1 is a graph showing an oil demand example of an OF cable line, FIG. 2 is a graph showing a change amount of oil during a transient in a healthy line, FIG. 3 is a graph showing a change in oil leakage, and FIG. FIG. 5 is a graph showing the amount of changed oil when oil is generated, FIG. 5 is a block diagram of the system of the embodiment, FIG. 6 is a block diagram of the terminal device, and FIG. 7 is a flowchart. 1 ... oil tank, 2 ... control station, 3 ... electric station, 4 ... oil station, 5 ... terminal equipment, 6 ... phone line switching equipment, 7 ... oil quantity sensor, 8 ... Alarm monitoring panel, 9: telephone line, 10: telephone line switching device, 11: master station.

Claims (1)

(57) [Claims] 1. An oil leakage in an OF cable line having an oil amount sensor for detecting an oil amount in an oil tank, and determining means for judging the presence or absence of oil leakage based on oil amount data detected by the oil amount sensor. In the detection system, the above-described determination means includes a temporal change in the oil amount decrease speed of the actually detected oil tank,
An oil leak detection system for an OF cable line, characterized in that oil leakage change is determined by comparing oil volume change characteristics that can be caused by a change in load current due to a change in load.