Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1997-09-19
1999-01-12
Wu, Daniel J.
Communications: electrical
Condition responsive indicating system
Specific condition
340540, 340657, 324520, G08B 2100
Patent
active
058595902
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fault sensor device and a fault sensing method, and more particularly, to the fault sensor device and the fault sensing method for sensing a fault such as a dielectric breakdown or a malfunction in electrical equipment.
BACKGROUND ART
FIG. 16 is a layout view showing the layout of a known protective relay for detecting an internal fault in an oil-filled transformer having a built-in on-load tap changer. Shown here are a transformer body 30, a radiator 31 mounted on the transformer body 30 for cooling oil, and an oil pump 32 mounted in the oil pipe running between the transformer body 30 and the radiator 31. Also shown are an oil purifier 33, a tap changer chamber 34, and conservators 35 and 36. Also shown are a Buchholtz's relay 37, a sudden pressure relay 38, and an oil flow relay 39. FIGS. 17 and 18 are diagrammatic cross-sectional views showing respectively the internal constructions of the Buchholtz's relay 37 and the sudden pressure relay 38 in FIG. 16. Since the oil flow relay 39 is identical, in construction and principle, to the Buchholtz's relay 37 its explanation is omitted here.
As shown in FIG. 17, a float 37a is provided within the Buchholtz's relay 37, and the float 37a floats or submerges with a floating support 37b depending on whether oil flow 201 is a rapid or slow. When the float 37a is submerged by a rapid oil flow, its associated contact points (contactors) 37c are closed, sending a signal externally via signal lines 37d.
As shown in FIG. 18, a partitioning plate 38a is provided in the middle of the sudden pressure relay 38, and the upper space above the. partitioning plate 38a forms a switch chamber 38b, in which a microswitch 38c is mounted. The partitioning plate 38a is provided with a hole in its center in which a bellows 38d is firmly engaged as shown, so that oil may not ingress into the switch chamber 38b. The partitioning plate 38a is provided with an equalizing capillary 38e which comunicates the switch chamber 38b with the interior of the bellows 38d to equalize both internal pressures. Disposed above the bellows 38d is a microswitch driving bellows 38f which expands upward by means of oil pressure 202 to activate the microswitch 38c when an oil pressure sudden or the like is generated.
The operation will now be discussed. When a fault associated with arcing takes place within the transformer body 30, the surrounding dielectric materials are quickly decomposed thermally and gasified, causing a rapid oil flow toward the conservator 36 and a sudden internal pressure rise. When the rapid oil flow takes place, the float 37a in the Buchholtz's relay 37 is forced to be submerged as shown in FIG. 17 by the dashed line, closing the associated contact points (contactors) 37c, whereby a signal is generated externally via the signal lines 37d. In the sudden pressure relay 38, the microswitch driving bellows 38f is expanded in response to the sudden oil pressure rise, whereby a contact closure signal for microswitch 38c is generated externally.
On the other hand, during normal operation, although a mild thermal expansion of oil takes place in the transformer body 30 as ambient temperature rises or a load increases, the resulting slow oil flow does not force the float 37a of the Buchholtz's relay 37 to submerge, and in the sudden pressure relay 38, the mild pressure change is equalized through the equalizing capillary 38e mounted between the bellows 38d and the switch chamber 38b, whereby the microswitch driving bellows 38f is not expanded upward, and a contact closure signal of the microswitch 38c is never generated.
Since the known protective relays in FIG. 16 are constructed as mentioned above, and the fault in the transformer body 30 is detected by the Buchholtz's relay 37 and the sudden pressure relay 38, the known protective relays suffer from the problem that when a sudden oil flow or a sudden pressure change takes place where the the oil pump 32 is started or stopped or in the event of an earthquake, the known protective relay
REFERENCES:
patent: 4547727 (1985-10-01), Tsui et al.
patent: 5726576 (1998-03-01), Miyata et al.
Mitsubishi Denki & Kabushiki Kaisha
Wu Daniel J.
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