Medium Voltage Conductors, Cable, Cable Joints, and Cable Terminations practice questions

Correct: A — Ozone-resistant insulation and shielding

315.44 requires both ozone-resistant insulation and shielding for solid dielectric conductors operated above 2000 volts in permanent installations. The 5000-volt nonshielded allowance is limited to industrial establishments with qualified maintenance and supervision, not all establishments, so it doesn't apply generally.

Correct: A — Conductor material, cable configuration, and installation method

315.60(C) splits ampacities across 20 tables by conductor material (copper/aluminum), cable configuration (single vs. three-conductor, triplexed vs. isolated), and installation method (air, conduit, duct, direct buried). Voltage alone doesn't select a table — the entire 2001-35,000 volt range shares this same set of tables. Copper and aluminum have separate tables because their ampacities differ, and installation method matters because heat dissipation differs by installation.

Correct: C — 900 mm (36 in.)

315.60(F)(7) caps the maximum depth to the top of direct-buried cables at 900 mm (36 in.). 750 mm (30 in.) is the maximum for duct banks instead, a common mix-up the closest distractor tests. The other depths aren't referenced in this section.

Correct: D — The installation date of the cable

315.16(A) requires the maximum rated voltage, the type letters, the manufacturer's identifying mark, and the AWG or circular mil size. Installation date is not a required marking item.

Correct: A — 35,000 volts

Per 315.32(A), Type MV cable is permitted on power systems rated up to and including 35,000 volts, nominal. The 600-volt and 1,000-volt options describe low-voltage wiring thresholds, not the MV cable ceiling, and 15,000 volts is simply below the actual limit.

Correct: B — Table 315.10(C)

Table 315.10(C), per 315.10(C), covers thickness of insulation for shielded solid dielectric insulated conductors rated 2001 volts to 35,000 volts — 25,000 V shielded falls squarely in that range. Table 315.10(B) is for nonshielded conductors only, and only up to 5000 V. Table 315.10(A) covers conductor application and insulation type, not thickness.

Correct: C — They must be shielded and identified for direct-burial use

315.36 requires direct-burial MV conductors and cables to be shielded, identified for such use, and installed per 305.15. A nonmetallic-jacket-only nonshielded cable doesn't meet this unless it falls under the narrow 2001-2400V metallic sheath/armor exception, and direct burial itself is the point of this section, not conduit-only installation.

Correct: C — By durable surface marking or a durably printed tag/label attached to the joint or termination

315.17(B)(1) and (B)(2) allow either durable surface marking or a durably printed tag/label attached to the joint or termination — one or both methods satisfy the requirement. Restricting to only surface marking or only a tag, or relying on separate paperwork, isn't what the code specifies.

Correct: B — The termination must be identified for use in direct sunlight

315.32(B)(1) specifically requires that Type MV cable joints and terminations exposed to direct sunlight be identified for that use. Meeting the 35,000-volt ceiling alone isn't sufficient, and submersion identification is a separate, unrelated requirement under 315.32(B)(3).

Correct: B — 315.60(D)(4)

315.60(D)(4) is the ambient temperature correction rule and hosts Table 315.60(D)(4) with the correction factors and equation. 315.60(D)(2) covers burial depth adjustment and 315.60(D)(1) covers grounded shields — both are different adjustment factors, not ambient temperature.

Correct: D — 40°C (104°F)

315.60(E)(2) sets the base ambient air temperature for the in-air ampacity tables at 40°C (104°F). The other values are common base ambients for other ampacity contexts but not the one specified for this section.

Correct: B — No decrease in ampacity is required, since the deepened portion is less than 25% of the total run length

315.60(D)(2)(a) allows skipping the ampacity decrease when the total length of deepened duct run is less than 25 percent of the total run length — 15% qualifies. Applying the 6% per foot factor (to the whole run or just the deepened part) is the 315.60(D)(2)(b) rule for when depth is deeper than the table basis generally, and it doesn't come with a backfill-material exception in this section.

Correct: B — Under engineering supervision

315.60(B) permits ampacity to be calculated using the general equation when done under engineering supervision. It is not limited to voltages above 46 kV, does not require AHJ pre-approval of the calculation itself, and isn't restricted to cases where no table exists.