7 CFR 1755.402 – Ground resistance measurements
(a) The resistance of the central office (CO) and the remote switching terminal (RST) ground shall be measured before and after it has been bonded to the master ground bar (MGB) where it is connected to the building electric service ground.
Terms Used In 7 CFR 1755.402
- Contract: A legal written agreement that becomes binding when signed.
(b) The ground resistance of electronic equipment such as span line repeaters, carrier terminal equipment, concentrators, etc. shall be measured.
(c) Method of measurement. The connection of test equipment for the ground resistance measurement shall be as shown in Figure 1. Refer to RUS Bulletin 1751F-802, “Electrical Protection Grounding Fundamentals,” for a comprehensive discussion of ground resistance measurements.
(d) Test equipment. The test equipment for making this measurement is shown in Figure 1 as follows:
(e) Applicable results. (1) For the CO and RST, the resistance after the bond has been made to the MGB electric service ground shall not exceed 5 ohms. Where the measured ground resistance exceeds 5 ohms, the borrower shall determine what additional grounding, if any, shall be provided.
(2) For electronic equipment, the ground resistance shall not exceed 25 ohms. Where the measured ground resistance exceeds 25 ohms, the borrower shall determine what additional grounding, if any, shall be provided.
(3) When ground resistance measurements exceed the ground resistance requirements of paragraphs (e)(1) and (e)(2) of this section, refer to RUS Bulletin 1751F-802, “Electrical Protection Grounding Fundamentals,” for suggested methods of reducing the ground resistance.
(f) Data record. Results of the CO and RST ground resistance measurements shall be recorded. A suggested format similar to Format I, Outside Plant Acceptance Tests—Subscriber Loops, in § 1755.407 or a format specified in the applicable construction contract may be used. Results of the electronic equipment ground resistance measurements shall be recorded. A suggested format similar to Format II, Outside Plant Acceptance Tests—Trunk Circuits, in § 1755.407 or a format specified in the applicable construction contract may be used. Data showing approximate moisture content of the soil at the time of measurement, the temperature, the type of soil and a description of the test equipment used shall also be included.
(g) Probable causes for nonconformance. Refer to RUS Bulletin 1751F-802, “Electrical Protection Grounding Fundamentals,” and Telecommunications Engineering and Construction Manual (TE&CM) Section 810, “Electrical Protection of Electronic Analog and Digital Central Office Equipment,” for possible causes of nonconformance and suggested methods for corrective action.