The information that is presented; has been assembled from SAES-P-116, 16-SAMSS-510, ANSI C37, GI-2.710, and related industry standards.
Figure 16 shows a Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. P-001 contains a checklist and data tables for visual, mechanical, and electrical inspections, as well as mechanical and electrical tests, of medium and high voltage switches.
Figure 16: Saudi Aramco Pre-Commissioning form, P-001,
Information, Formulas, and Tables for Use in Evaluating the Results of Insulation Resistance (Megger) Tests
The results of all commissioning megger tests that are performed must be documented on the appropriate Saudi Aramco pre-commissioning form. A short time (1 minute) megger test is performed.
Figure 17 shows the recommended megger test voltages for various equipment voltage ratings.
Equipment Recommended
Megger Voltage Rating Test Voltage
100 - 250 500
251 - 600 1000
601 - 2500 2500
5000 + 5000
Figure 17: Recommended Megger Test Voltages
Figure 18 provides bolt torque values for bus connections.
Bolt Size Tightening Torque
#8 - 32 10 - 15 inch pounds
#10 - 32 15 - 20 inch pounds 1/4 x 20 5 - 7 foot pounds 5/16 x 18 10 - 12 foot pounds
3/8 x 16 18 - 20 foot pounds 1/2 x 13 40 - 50 foot pounds Figure 18: Bolt Torque Values for Bus Connections
AC or DC Hi Pot Tests
The ac and dc hi pot tests are high potential voltage tests that are conducted phase to ground and phase to phase. The tests are conducted from both the line and the load side of the open breaker contacts. The ac and dc hi pot test voltages must be in accordance with the manufacturer's recommended values. When the manufacturer's recommended values are not available, the maximum voltage values in the table in Figure 19 should be used:
Equipment Rated kV Test Voltage kV
AC DC
2.5 5.0 9.0
5 9.35 16.0
15 26.0 44.0
25 43.0 73.0
35 60 102.0
Figure 19: Table of Hi Pot Test Values
For the dc hi pot test, apply an initial voltage step of about one-third of the recommended maximum voltage and maintain the initial voltage for ten minutes. After the initial ten-minute test, the dc test voltage is increased in ten uniform steps up to the maximum recommended dc value.
Each step should be held for one minute.
For the ac hi pot test, increase the test voltage at a rate of 1 kV per second until the maximum recommended test voltage is reached. Field test voltages are determined by the following: ac test volts = 0.75 x (2.0 x rated voltage + 1kV).
Information, Formulas, and Tables for Use in Evaluating the Results of Hi-Pot Tests
During the performance of hi-pot testing, the test should be stopped if one of the following situations occurs:
• The duration of the test has expired.
The following are the characteristics of a satisfactory hi-pot test:
• The leakage current decreases over time.
• The leakage current increases on a straight line as voltage is increased. No "knee"
is noticeable in the leakage current curve.
An example of hi-pot test data is shown in Figure 20. Figure 20 shows both good and bad insulation test data.
Figure 20: Example of Hi-Pot Testing (Good and Bad Insulation)
The following is an excerpt for GI 2.710, New Construction Check List Example, that illustrates the overall checklist and sign-off for major pieces of electrical equipment.
3. Electrical Equipment
All substations, power cable, electrical Construction Agency equipment, including lighting and wiring,
to be checked for proper application,
operation, and grounds. Distribution panels, switches properly identified, and all energization certificate requests signed.
Power Distribution Dept.
Project Inspection Commissioning (Note 1)
Figure 21 shows an excerpt from GI 2.710, General Instruction Manual, that illustrates the inspections and tests that should be performed in major pieces of electrical equipment prior to the turnover of a facility.
Figure 21: GI 2.710 Excerpt
GLOSSARY
BIL The basic impulse insulation level (BIL) is the reference impulse level, expressed in full wave kilovolts, that the equipment can withstand without a flashover.
dielectric absorption The ratio of two timed insulation resistance readings (such as a ratio 60-second reading that is divided by a 30-second reading).
grounding switch A ground switch is a mechanical switching device by means of which a circuit or piece of apparatus may be electrically connected to ground for maintenance and safety reasons.
group operation A group operation is the operation of all poles of a multiple-pole switching device
(ganged operation) by one operating mechanism. Group operation is in contrast to single pole operation in which the number of operations required to reposition the device is equal to the number of poles.
load current The highest rms current (in amperes) between unity and 0.8 power factor (lagging)
interrupting rating that a loadbreak switch must be required to interrupt at the rated voltage and frequency for the expected operating life of the switch.
maximum direct The rms total current, which includes the transient direct-current
current component.
nominal system The nominal system voltage refers to the general equipment voltage voltage class designation.
polarization index The ratio of a ten-minute insulation resistance reading divided by a one-minute insulation resistance reading.
rated continuous The amount of current that can be continuously carried by the equipment without
current at 60 Hz exceeding the equipment allowable temperature rise.
rated maximum The highest rms voltage for which the equipment is designed, and it is voltage the upper limit for operation.
rated voltage The highest nominal system voltage on which the equipment is intended to be applied.
rated withstand The voltage that the equipment must be able to withstand without voltage flashover or other electric failure.