PROBLEM IN COMMISSIONING PROCESS OF 125VDC STATIONARY BATTERY IN LAM-LUK-KA SUBSTATION

Transcription

1 PROBLEM IN COMMISSIONING PROCESS OF 125VDC STATIONARY BATTERY IN LAM-LUK-KA SUBSTATION K. Paramate, Electricity Generating Authority of Thailand, , ABSRACT This paper presents the problem in commissioning process of 125VDC stationary battery in Lam-Luk- Ka substation which has one string of 58cells stationary battery. This construction project was a turnkey project and contractor has selected a battery from manufacturer, while it has never been used in EGAT. In this commissioning was revealed numerous of problems such as the test results of stationary battery that do not meet the standard, The conclusion of each process is quite slow due to many parties concerned. And in the hustle of the schedule in the power supply system. The problems and obstacles, as mentioned above, enabling organizations to gain experience and knowledge to be used as a guideline to action for the commissioning phase in construction projects that will be occur more in the future. KEYWORDS: Commissioning, Stationary Battery, Substation 1. Introduction These days, electricity demand is becoming more significant increase in year over year. In order to provide a maximum confidence in terms of stability and reliability in a power supply especially in the metropolitan area where the most of important business, industry and economy of the country, as well as to prevent unplanned power failures or electricity outages. Therefore EGAT has required to ensure that electric very closely matches the demand by construct a new power plant, substation and transmission line in order to meet sufficient on increasing the demand of electricity. In terms of construction, there are a commissioning phase procedure which is very important since the idea of intensive inspection in commissioning phase could be reduced a load of maintenance Lam-Luk-Ka substation is one of the substation that was constructed to provide a maximum confidence in terms of stability and reliability in a power system. Which located in Pratumthani, in responsibility of Metropolitan Area Operation Division. Lam-Luk-Ka substation is 230/115kV Gas Insulated Substation type consist of Power Transformer 300MVA, 230/115kV 3 units. Lam-Luk-Ka substation has one string of stationary battery and each string contain 58 cells. This construction project was a turnkey project and contractor has selected a battery from manufacturer, while it has never been used in EGAT. There are OPzS type, nominal voltage 2 volt and nominal capacity This clause shall consider carefully for the specification and capabilities of the battery. During inspection of the battery, there are step procedures for testing battery such as Visual Inspection, Discharge Test to measure capacity of the battery, Measuring the specific gravity and the volt/cell while Equalize Charge and Floating Charge and Measurement Impedance of batteries in each Cell, if it was found that the battery fails the test, a plan could be revised in a problem solving meeting to find the best solution. Figure 1: Stationary Battery 125VDC in Lam-Luk-Ka substation

2 2. Main Contents 2.1 Stationary Battery Stationary lead acid battery is Battery that use in substation. Normally Stationary battery will use at 125VDC. In one string contain of 58cell and each cell have nominal voltage at 2volt, Float Charge Voltage around 2.23±0.05 volt/cells, Equalize Charge Voltage around 2.35±0.05 volt/cells. 2.2 Testing and Commissioning Procedure Figure 2: DC Supply in Substation Standard and Specification In the commissioning process, EGAT was follow to Specification from Transmission System Engineering Division, EGAT, Specification No.310 Stationary Battery which covers the general requirements for design, manufacture, test and supply of the stationary battery. Moreover, EGAT was follow to Standard EGAT TS EGAT Testing Standard Stationary Battery which cover Test procedure, Test item and standard values for stationary lead acid battery Test Item for Stationary Battery Visual Inspection Before commissioning all cells/blocks must be inspected for mechanical damage, cells must be connected with the correct polarity and connectors firmly seated. If necessary, the terminal covers must be put on. With charger off and loads isolated, connect battery to the direct current power supply, maintaining correct polarity (positive terminal to positive post) Discharge Test or Capacity Test Equalizing charge battery until specific gravity and volt/cell are at steady state Before doing Discharge test Discharge current equal to Amp. Hour rate divided by Hour rate Using time for Discharge 100% of Hour connect battery to Load discharge resistor During Discharge test must to record specific gravity and volt/cell in every hour until the final hours Impedance Test Impedance Test is the test method to follow the condition of battery when the same state at full charge Impedance/Cells should not deviate from group over than 10%.

3 2.3 Problem in Commissioning Problem of Battery Room During the construction of Lam-Luk-Ka substation. We found that there was constructed a window glass in the battery room, however from some experience, standards and specifications related to the construction of a battery rooms. Practically battery room should be closed room without windows installation in order to prevent heat from the sun s radiant throughout the battery, which could be affected the ability to control the temperature inside the room. However, when an inevitable for the window installation, these should be required a sunblind installation to exposure sunlight. Figure 3: Battery room, which found that the construction of windows glass From the information above, EGAT request to the contractor to correct it. The contractor was resolve by building a brick wall instead of the window Figure 4: Battery room after correction Problem of Station Battery 125VDC First Commissioning When the contractor has already done with the battery room. They had done the Discharge Test and deliver the test result to EGAT. The result has found that battery can pass Discharge Test, on the other hand when the Equalize Charge and Floating Charge found the volt/cell was abnormally high and the deviation was over tolerance of the manufacturer. Table 1 shows the value of volt/cell when Equalize Charge and Floating Charge. To find the best solution for the project by setting up the meeting for clarify the issues. It was concluded that the manufacturer would be resolved by discharge to 60% of the battery capacity and then fully charge. Then adjustment the specific gravity. However, after the manufacturer has complete resolved and measure it again, volt/cell still unstable. After this problem, the manufacturer presents the last plan to repair this battery by follow this plan

4 During repairing process the manufacturer will provide mobile battery and will calculated capacity of load in Lum-Luk-Ka substation to supply 125VDC The manufacturer will bring back all string of battery to manufacturer s factory to recondition In the process of repairing the manufacturer has grouping the battery by volt/cell into two group. Group 1 is volt/cell over than standard (19 Unit) and Group 2 is volt/cell meet the standard Group 1 will discharge at 60% and recharge at current 0.05CA = 5Hr and adjust to 0.1CA = 10Hr during charging and record specific gravity and thermal every hour until battery full charge Group 2 will charge to full charge by adjust voltage charge to 2.35±0.05 volt/cells Gather Group 1 and Group2 and charging to balance voltage by adjust voltage charge to 2.33±0.05 volt/cells Return all string of battery back to Lam-Luk-Ka substation Table 1: volt/cell was abnormally high and the deviation was over tolerance of the manufacturer Second Commissioning After the manufacturer has complete resolved. The manufacturer transport all battery back to Lam-Luk-Ka substation and ask for commissioning again. In the new commission process EGAT found that the specific gravity in the prior of the process Discharge Test was not meet the standard criteria. EGAT provides manufacturers clarify and find a solution. The manufacturer resolve by recharging include adjust specific gravity Third Commissioning After the second resolved, During the Discharge Test the specific gravity over scale from the manufacturer s instrument, therefore EGAT request to stop the Discharge Test and test again with new one of specific gravity instrument which has certificate.

5 Last Commissioning In the last commissioning EGAT told the manufacturer that if this time the Discharge Test was not pass EGAT will reject all sting of battery from this manufacturer. In this commissioning the manufacturer brings the new one of specific gravity instrument with the certification. Battery can pass Discharge Test, volt/cell and specific gravity are meet the standard criteria. 3. Result The result of the commissioning has found that battery can pass Discharge Test, on the other hand when the Equalize Charge and Floating Charge found the volt/cell was abnormally high and the deviation was over tolerance of the manufacturer. To find the best solution for the project by setting up the meeting for clarify the issues. It was concluded that the manufacturer would be resolved by discharge to 60% of the battery capacity and then fully charge. Then adjustment the specific gravity. After the manufacturer has complete resolved. In the new commission process EGAT found that the specific gravity in the prior of the process Discharge Test was not meet the standard criteria. EGAT provides manufacturers clarify and find a solution. After the second commissioning, the manufacturer has resolved again but during the Discharge Test the specific gravity over scale from the manufacturer s instrument, therefore EGAT request to stop the Discharge Test and test again with new one of specific gravity instrument which has certificate. In the last commissioning the that battery can pass Discharge Test, volt/cell and specific gravity are meet the standard criteria. 4. Conclusion In this commissioning was revealed numerous of problems such as the test results of stationary battery that do not meet the standard, the conclusion of each process is quite slow due to many parties concerned. And in the hustle of the schedule in the power supply system. The problems and obstacles, as mentioned above, enabling organizations to gain experience and knowledge to be used as a guideline to action for the commissioning phase in construction projects that will be occur more in the future. REFERENCES [1] IEEE Recommended Practice for Installation Design and Installation of Vented Lead-Acid Batteries for Stationary Applications, IEEE [2] IEEE Recommended Practice for Installation Design and Installation of Valve-Regulated Lead-Acid Storage Batteries for Stationary Applications, IEEE [3] IEEE Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead Acid Batteries for Stationary Applications, IEEE [4] EGAT Testing Standard Stationary Battery, EGAT TS [5] Specification No.310 Stationary Battery, Transmission System Engineering Division, EGAT [6] Design Guide for Power Station Battery Rooms, Eskom