Caveat Lector: Although great care has been taken in the compilation of the information contained on this web site, the authors are not liable for the accuracy in terms of error or omission. The information on this web site is subject to change without notice and without obligation on the part of the authors. The authors shall not be liable for technical failures or for failures beyond their control. Some posts may contain authors' personal opinions and views and the authors do not represent any company, corporation or institution.

Saturday, June 4, 2016

Non-Tripping Operation of a 69kV Power Crcuit Breaker

I posted a problem in the REE forum regarding the non-operation of a 69kV power circuit breaker. Here is the discussions made about the problem and what really happened on the breaker as found by maintenance group.

ACCESS OF FAULT DATA: NARI NR PCS-974 (Power Transformer Non-Electrical Protections Relay)

Below is the procedure in the access of fault indications of the NR NARI Transformer Non-Electrical Protection Relay PCS-974. This post only discusses the access of relay indications and readings especially during faults or retrieval of data.

ACCESS OF FAULT DATA: NARI NR PCS-978 (for Power Transformer Electrical Protection)

Below is the procedure in the access of fault indications of the NR NARI Transformer Electrical Protection Relay PCS-978. This post only discusses the access of relay indications and readings especially during faults or retrieval of data.

Saturday, November 7, 2015


Below is the procedure in the access of fault indications of the SEG MRI3 Overcurrent Relay. Most substation engineers are limited in the access of relay indications and readings especially during faults or retrieval of data since there is a separate group that handles relay testing and setting.  I am not familiar with the latest relay tester already that is why I could not include relay setting and testing.

Monday, November 2, 2015


Below is the procedure in the access of fault indications of the ABB SPAA 331C Overcurrent Relay. Most substation engineers are limited in the access of relay indications and readings especially during faults or retrieval of data since there is a separate group that handles relay testing and setting.  I am not familiar with the latest relay tester already that is why I could not include relay setting and testing.



Monday, July 9, 2012

Tripping of Customer 69kV Line ( July 5, 2012 at 1934H )

Below is my root cause analysis (RCA) for the tripping of our 69kV Line. Since I could not speak for the Test and maintenance section-Relay Group, I presented the root cause using simple calculation and analysis. Please leave comments below for the improvement of this RCA.

Thursday, March 8, 2012

Root Cause Analysis: Oil Trace at Phase B of 115kV Current Transformer


      February 28, 2011, 1705H- The Senior Engineer on-duty , observed the oil trace on the head of phase B of 115kV current transformer while doing his daily routine inspection.

Tuesday, November 1, 2011

Measurement of No-load Loss and Current for Power Transformer

Here are the procedure for testing of no-load loss and current for Power Transformer. This procedure has been simplified and given by the Hyosung manufacturer for observation purposes during factory acceptance test at their factory.

Tuesday, October 25, 2011

Solution Against Transformer Explosion: Transformer Protector (Last Part)

Below is a diagram showing the different parts of the Transformer Protector system. The different parts are labeled which makes the operation easier to understand.

Tuesday, October 18, 2011

Solution Against Transformer Explosion: Transformer Protector

Mr. Justin Gong emailed me informing about their product which is the Transformer Protector. This product can prevent power transformer explosion and can extinguish the fire in a matter of few minutes by using Nitrogen, which is claimed to be a better fire extinguisher for fires involving insulating oils compares to water or cabon dioxide. There has been a few revisions to the original text and below is the excerpt of their product:

Sunday, September 11, 2011

Current Transformer Nameplate Data (Part 2)

I have posed before the commonly data on a current transformer nameplate. Listed below are the data and its brief description:

IEEE C57.12.90-2006 Test Code for Liquid-Immersed Transformers (series 1)

I have obtained a photocopy of the IEEE Standard C57.12.90-2006 Test Code for Liquid-Immersed Distribution, Power and Regulating Transformers. I am posting part by part of the standard and the posts will serve as my reference notes.

Winding Resistance Testing for Power Transformer

Measurement of winding resistanceThe purpose of testing the winding resistance is to detect and confirm faults in the transformer winding.  The standard criteria being used before is that the standard deviation of three readings must not exceed 0.5. However, the new IEEE standard C57.12.90, there is no specific requirements for the resistance but will serve as reference for future testing.

Transformer Ratio Test and Phase Displacement Check

In the measurement of power transformer voltage ratio, the different taps of the tap changer are tested compared to the nameplate rating. If the testing is from high voltage side and low voltage side, then each tap position is tested against its nameplate rating. Each tap position has corresponding nameplate tap voltage and ratio. During the testing, the measured ratio and its corresponding error are determined.

Sunday, September 4, 2011

Emergency Shutdown of 50 MVA Transformer due to Oil Leak at the Base of Ground-Connection Terminals for Transformer Active Parts (Core Clamps and Core Laminations)

Our power transformer in our substation has been plagued by various oil leak problems. Considering that the transformer is still 15 years old, it is still considered at its peak performance. But some of its parts had failed already on which the insulating oil inside had found its way to leak. This article is about another weak part of the power transformer that may be a probable source of oil leak.

Monday, August 8, 2011

Factory Acceptance Test: Nantong Hyosung Transformer Co., Ltd. (Part 3)

We can only take pictures of the transformer for FAT but we are not allowed to take pictures of the five areas of EHV workshops (coiling area, insulation processing area, core processing area, active part assembly area, and final assembly area) including other products inside.
Below are some of the shots during testing of the power transformers:

Factory Acceptance Test: Nantong Hyosung Transformer Co., Ltd. (Part 2)

The continuation of my report is summarized below:

B) Spare parts for the their products are readily available from Nantong Hyosung. They can deliver spare parts, including bushings, one month after the order has been placed.
C) The company usually give 12-month warranty of their product after energization or 18 months after delivery, whichever comes first.
D) Nantong Hyosung Tansformer Co. Ltd. can provide financing to the buyers of their products.
E)  We took a tour on transformer manufacture, testing and inspection after the presentation.
-Among their equipments include horizontal and vertical winding machines, slitting lines for silicon steel sheets, core binding machine, air-cushioned vehicle, 400-ton crane and large stacking station.
-The EHV workshop has five areas. These are: coiling area, insulation processing area, core processing area, active part assembly area, and final assembly area. Their factory also boasts its modern EHV testing center where the transformers are tested to determine if they pass the customers' requirements and limits.

Factory Acceptance Test: Nantong Hyosung Transformer Co., Ltd.

Below is my report to our Human Resource Department for the Factory Acceptance Tests that I had witnessed at Nantong Hyosung, China. Specific details of the testing of power transformers will follow.

Date: JULY 29 - AUGUST 5, 2011

Wednesday, July 20, 2011

Current Transformer Nameplate Data

The nameplate of current transformers contains basic information about the transformer. The most common data in the nameplate are listed below:

Tuesday, July 19, 2011

Autotripping of 50MVA Transformer due to Earthquake

We had experienced a shallow earthquake which caused the tripping of our 50MVA Transformer. Below is the incident report of the tripping:

Tuesday, June 28, 2011

Power Circuit Breaker Closing Circuit Diagram (substation equipment operation)

The basic closing circuit for a power circuit breaker is illustrated below. Closing circuit consists of miniature circuit breaker (CB2) that protects the closing coil from overcurrent. Tracing the first node is the push button PB1 52C. This is the push button for local closing of the power circuit breaker.

Power Circuit Breaker Trip Circuit Diagram (substation equipment operation)

The basic trip circuit for a power circuit breaker is illustrated below. The trip and close circuit of power circuit breakers is just a simple DC circuit. Trip circuit consists of miniature circuit breaker (CB2) that protects the trip coil from overcurrent.

SCADA : Supervisory Control and Data Acquisition (Part 1) - Wonderware (Intouch10.0)

SCADA stands for Supervisory Control and Data Acquisition. From the meaning itself, SCADA is important for controls of equipment and data gathering of different parameters of gauges and meters. SCADA is a process management tool for data management, user-control interface and visual window. As data management, it is a powerful tool to manage and process data.

Friday, June 10, 2011

substation maintenance: Dissolved Gas Analysis for Insulating Oils

Oil-filled high voltage power equipment particularly power transformer have useful life. In order to maximize its useful life, preventive maintenance is being conducted regularly to abate equipment failure before its specified life span. One way of determining equipment failure is through dissolved gas analysis (DGA) of high voltage equipment. Let us take for example the power transformer. Big power transformers usually has a useful life of 50 years.

Wednesday, June 8, 2011

Conclusion: Replacement of Battery Cells with Low Specific Gravity

We had adjusted before the float voltage charge of the 125 Vdc battery bank no. 1 of our substation (please see related posts: Low Specific gravity... and Update on Low....) inorder to improve the specific gravity of its four battery cells.  Upon monitoring the voltage and specific gravity of the affected cells, cell nos. 1 and 48 had improved their specific gravity results. While the voltage of each battery cells are all normal, this is not conclusive that the battery cells are in good condition.

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

Saturday, April 30, 2011

Update on Low Specific Gravity Lead Acid Batteries

In my last post, I have recommended three action plans for Station Battery monitoring, namely replacement of the battery cells with low specific gravity,formulation of monitoring logbook for electrolyte level for station batteries, and Installation of ACU for Battery Room. So far, Airconditioning System and monitoring and topping-up of electrolyte level were implemented. We cannot replace the affected batteries since there are no spares left. The spare batteries of district one substation were all used when a cell of a battery bank exploded at a particular substation.

Tuesday, March 29, 2011

Low Specific Gravity of cells of 125 VDC Battery Bank

I. Background of the Problem:
March 24, 2011
a. The Substation Engineer-on-duty conducted monthly testing of station batteries. Our 125 VDC Battery Bank is composed of sixty lead acid battery cells. Battery testing include voltage, temperature and specific gravity measurements for the 125 VDC, 48 VDC and 12 VDC battery cells.
b. He noticed that the specific gravity of some cells of 125VDC battery bank 1 were below the normal value which is 1.215. He then put 125 VDC Battery Bank 1 to equalizing charge for 24 hours.

Tuesday, March 22, 2011

lead-acid battery explosion and prevention

Battery bank of power substation is very critical since it serves as standby power supply for the high voltage equipment and its relays to be operated so that power can be restored in case of massive blackout or total loss of power. Lead-acid batteries are the most common type of batteries used in substation battery banks. Advantages include the ability to supply high surge current, large power to weight ratio, relatively cheap, easy maintenance and long useful life.Hence, maintenance of battery banks are conducted monthly to ensure its effective and reliable operation.

Sunday, March 13, 2011

power bill rates computation: customer billing sample

Below is the sample computation of a non-firm customer with motor loads. I will not include the taxable service, non-taxable service and franchise tax computations so that power bill computations will be presented as simple as possible. There are also other charges that are not included like the metering charge, force majeure charge, power factor adjustment charge, the reactive power support charge, and universal charges.

Saturday, March 12, 2011

Sample Applicable Power Service and Ancillary Rates

Just to share the sample ancillary Rates for the Billing month of February 2011, please search the internet for real-time ancillary rates given by the utility providers. Please use the table as reference guide only. The rates are subject to change without prior notice.

Tuesday, February 22, 2011

Root Cause Analysis: Stuck-up Worm Gear for Spring Charge Mechanism of 69kV Power Circuit Breaker (part 2)

This is the continuation of my previous post. We did some extreme measures but after re-energization of the line, it was worth it.
1. At 1750H, temporarily bypassed the Power circuit breaker 1 so that the line could be energized.

Root Cause Analysis: Stuck-up Worm Gear for Spring Charge Mechanism of 69kV Power Circuit Breaker

I would like to share the substation equipment trouble that happened in our substation last February 15, 2011. We conducted maintenance on 69kV breaker and during energization of the line, the breaker failed to close after series of attempts. After series of troubleshooting, we found that the worm gear for spring charge mechanism was stuck on its bushing. Below is the full text of my report:

Sunday, October 17, 2010

Blackout Restoration Procedure (Substation Operation and Maintenance)

Since a super typhoon is expected to make a landfall here in the Philippines tomorrow, utmost preparation is being implemented by the Substation and Transmission Line personnel. Previous typhoons have caused blackouts so a possibility for another blackout is likely to happen.

Typhoon Preparedness Checklist: Preparing for the Coming of Super Typhoon Juan (International Name: Megi)

As we brace ourselves for the incoming Super Typhoon Juan (international name: Megi), here are a few checklist that we have implemented to minimize the damaging effect of the passage of typhoon to our Substation:

Tuesday, October 12, 2010

Root Cause Analysis: Preventing the HV Current Transformer from Exploding

The golden rule of high voltage instrument transformers is that " Never open a Current Transformer, and Never short a Potential/ Voltage Transformer". In this case, a current transformer has been left open because one slide of the terminal block was at open position. Probable cause is that the last maintenance group which conducted testing on the current transformer forgot to slide back the terminal blocks after they have isolated it. Anyways, the report submitted regarding the problem is stated below:

Monday, October 4, 2010

Emergency Shutdown of Power Circuit Breaker (Arcing due to Insulator Cleaner)

I. Background of the Problem:

115kV Power Circuit Breakers were scheduled for maintenance on September 29, 2010. The breakers were maintained one at a time. The testing for Breaker 1 started at 0601H and ended at 1024H. The testing for Breaker 2 started at 1026H and ended at 1152H. Initial results of the tests were satisfactory for both breakers.

Saturday, September 25, 2010

Power Transformer Electrical and Mechanical protection (Part 2)

This will be the second part of the table about Power Transformer Electrical and Mechanical Protection.

Thursday, September 23, 2010

Power Transformer Electrical and Mechanical protection

While cleaning some of my old stuff, I found a table about Power Transformer electrical and mechanical protection. This had been used as reference for basic troubleshooting with regards to Power Transformer Protection. This had been my guide when I was still working at Transco. Nevertheless, some of the entries needs to be updated so that it may be applicable to other substations.

Sunday, August 8, 2010

Power System Analysis: Tripping of Transmission Line after restoration of Power

I am going to share my analysis on the event that happened recently on our substation. For an overview, there are four substations in radial system, first is the Substation A, next are Substations B, C, and D. The source of power is from substation A going to B, going to C and lastly to D. The distance relays of substation A to C are radially connected. It means that no looking back relay is installed on adjacent substation.

Sunday, August 1, 2010

troubleshooting defective jet water pump motor for drainage system

This morning, our jet water pump cannot draw water out in the Cable Trench Drainage at the substation. In just one year of operation, it baffles us that the water pump is already unusable. Anyways, here are the step by step procedures that we did in trying to repair our beloved pump:

Friday, July 30, 2010

preparation of monthly reports (Part 2)

This is the last part of the topic under monthly reports. Another report that is being prepared monthly is the Transformer load profile(TLP). The TLP will provide the peak load of the Transformer/s and its corresponding date and time.

Wednesday, July 28, 2010

Testing for grounded DC supply in an Ungrounded DC System

In an ungrounded DC System, the positive and negative terminals are not directly connected to ground while in the Grounded DC System, one of either terminal is connected directly to ground. Usually, this DC System is created when the configuration of the AC voltage source connected to the rectifier is in delta-connection and the junction between the rectifiers is not connected to ground.

Monday, July 26, 2010

preparation of monthly reports (Part 1)

Every last Monday of the month, monthly reports are required in our substation. There are at least nine reports to be submitted at our main office were trends and different values are tallied. I am going to discuss all of the reports that we are required to submit.

Friday, July 23, 2010

substation control room building leaks

we have been experiencing leaks from the cracks of the concrete gutter of our substation control room building. Since the building is still part of the substation, I will discuss some of our corrective actions which may help others or open to suggestions from the readers.

Setting or resetting of Frequency Relay at Electric Power Substation

Yesterday was the scheduled setting of Frequency Relay on our substation. Frequency Relay is a device that monitors the increase and decrease of frequency which can isolate a certain feeder if the frequency is unstable.

Monday, July 19, 2010

How to prepare a Substation Daily logsheet

This is to differentiate the logbook to a logsheet. Normally, the logbook entries consist of phrases and sentences which describe the activities that happen in a substation.

Sunday, July 18, 2010

substation engineers and operators guide: logbook

A logbook is a listing of all events and activities done in the substation. It serves a reference by the operators and engineers and a record book for easy retrieval of historical activities and data.

Sunday, January 4, 2009