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Tuesday, May 31, 2011

SF6 Gas Leak Detector (Dilo) - Substation Maintenance

SF6 gas is one of the common insulating medium of high voltage power circuit breakers. Eventhough this gas is odorless, colorless, and non-toxic, it is one of the greenhouse gases that contribute to the destruction of ozone layer. Therefore, proper handling of this gas must be done inorder to minimize, or eliminate the escape of this gas to the atmosphere. We can also check the integrity of the pipings of SF6-insulated power equipment so that no SF6 is leaking. One test unit that is used in detecting SF6 leak is the SF6-Gas Leak Detector (model no. 3-033-R002) by Dilo.

Sunday, May 29, 2011

Battery Load Capacity Test Torkel 720 (Part 2)

After which we turn on the miniature circuit breaker on the tester which acts as the switch of the test unit to start the test. We record the total voltage of the battery bank every test set. The test automatically stops after the full load is reached. After which the load will be left connected for another ten minutes, then the battery charger will be turned on.

Battery Load Capacity Test Torkel 720

Battery Load Capacity Test (BLCT) is conducted to standby power supply, usually battery banks, inorder to determine if they can give stable power to connected loads in case there is a blackout or total loss of power. This test also determines if the battery bank can still perform according to their rated ampere-hour. The battery banks to be tested should be properly charged before the conduct of the test. The batteries must have correct electrolyte levels, battey caps must be secured, and the cells should be clean and free from foreign particles so that the result will be accurate.

Tuesday, May 24, 2011

Substation maintenance: oil sampling for dissolved gas analysis

Oil sampling is being done to our 50 MVA Power Transformer quarterly. The maintenance group draws out power transformer oil sample for analysis. Most of the time, they draw the oil from gate valve located near the base of the transformer main tank. But for power transformer with Dissolve Gas Analyzer installed like in our substation, they just connect an adaptor to a port dedicated for oil sampling. The drawn-out oil must not contain bubbles inside the syringe as these bubbles may give false results on the test data.

Monday, May 23, 2011

Substation Maintenance: Degasifier Flow Sequence


Sunday, May 22, 2011

Replacement of voltage transformer (high voltage)

Voltage Transformers are instrument transformers that convert high primary voltage (usually 69 kV and above) to low secondary voltage (usually 115 V and 66.4 V)for utilization of other instruments like protective relays and meters. These instrument transformers are also known as potential transformers. The most common insulation of these instrument transformers is insulating oil.

Substation Maintenance: Oil purifier / Degasifier

High vacuum oil purifier, or commonly known as degassifier, is a machine that purifies the insulating oil of high voltage equipment. Degassifier consists of heaters, vacuum pump, centrifuge pump and filters that work together inorder to improve the insulating capability of the HV equipment insulating oil.

Wednesday, May 4, 2011

low energy reading on EIG statistical meter (part 2)

Since the load of the customer is very low we are thinking about replacing the current transformer installed on the feeder. Even the metering group that came to troubleshoot the problem was bent on replacing the CT. They attached a tester that read the secondary currents going to the meter. On their tester, it read 0.8 amperes on three phases but on the EIG meter, it displayed zero amperes. After the tests have been made, we decided to adjust the setting on the EIG meter to display readings in terms of kilowatts in terms of megawatts. 

low energy reading on EIG statistical meter (part 1)

We have been monitoring the statistical meter of our customer for the past three months. This is because the energy reading is very low compared to the downloaded billing meter at the customer's end. We have been proposing that the current transformer used at our side be replaced with a current transformer of lower CT ratio. The CT ratios available in our unit are 1000:5 and 500:5. The customer has a 4 MVA power transformer at their substation with seven 350-kW motor pumps. Considering the rating of their power transformer at full load with unity power factor, their full load current will be