Specifications

PIP ELTFT01
Field Inspection and Testing of March 2001
New Electrical Equipment
Process Industry Practices Page 8 of 23
5.7 Minimum acceptable polarization index for the dielectric absorption test on medium-
voltage motor circuits is 2.0. For transformers, the minimum acceptable polarization
index shall be according to the manufacturer’s recommendations. If manufacturer’s
data are not available, the acceptance test results will serve as baseline data for
future tests.
5.8 Maximum contact resistance for medium-voltage breakers and contactors shall meet
manufacturer’s recommendations. If manufacturer’s data are not available, the
resistance shall not vary between phases by more than 25 percent.
6. Grounding Systems
6.1. Below Ground
The following checks and inspections shall be performed before backfilling or
concrete pouring:
6.1.1 Check that grounding system is in compliance with drawings and
specifications.
6.1.2 Check ground well installations for accessibility to ground rods.
6.1.3 Inspect all underground splices.
6.1.4 Inspect all internal foundation ground connections.
6.1.5 Check ground grid and ground loop wire sizes and color identification.
6.2. Above Ground
6.2.1 Check that grounding system is in compliance with drawings and
specifications.
6.2.2 Check all connections for tightness.
6.2.3 Check installations for mechanical protection of ground wire.
6.2.4 Test each ground loop segment for continuity between ground wells or
ground terminal bars.
6.2.5 Test each main ground grid for resistance to earth using the fall of potential
method. All connections to other ground grids shall be disconnected while
performing this test.
6.2.6 Individual tests of resistance to earth shall be performed using the fall of
potential method for the following equipment after their connection to the
ground grid:
1. Electrical system neutral grounding locations
2. Switchgear ground bus (all voltage levels)
3. Grouped motor control centers ground bus (all applicable voltage
levels)