Overview

Medium voltage systems, typically operating at voltages of up to 35 kV, play a crucial role in distributing power to large consumers like commercial and industrial buildings. Due to the high voltages involved, specialized cables, cable joints, and terminations are vital for effectively regulating power flow within these systems. However, the performance of such equipment can be significantly affected by additional environmental stresses found in specific applications and locations. Recognizing the importance of addressing these concerns, the NEC introduced Section 315.32 in its 2023 edition. This section outlines specific conditions and guidelines for using medium voltage (MV) equipment in various environments and applications with voltages up to 35,000 volts. By providing clear guidelines, this update aims to ensure the safe and reliable operation of medium voltage systems in diverse settings.

Applying the 2023 Code

Medium voltage cables, cable joints, and terminations are integral components for maintaining and managing power flow in systems operating at voltages up to 35,000 Volts. These equipments play a crucial role in ensuring reliability, safety, and efficiency within medium voltage (MV) distribution systems, primarily due to their higher insulation ratings and increased voltage tolerance. Despite their robust design, MV systems are often deployed in environments characterized by increased environmental stresses, including UV radiation exposure and extreme weather conditions. Such factors can significantly impact the performance and longevity of MV equipment, potentially leading to system failures. NEC Section 315.32 “Uses Permitted for Type Medium Voltage Cables, Cable Joints, and Terminations” has identified and emphasized various applications and locations where MV cables, cable joints, and terminations may be installed. By adhering to these regulations and implementing appropriate protective measures, the integrity and performance of MV equipment can be preserved across a wide range of settings, thereby minimizing the risk of operational disruptions and ensuring the continued functionality of MV distribution systems.

What’s New for the 2023 NEC?

2020 NEC

In the 2020 NEC, no reference can be found for the uses permitted for cable joints and terminations.

2023 NEC

In the 2023 NEC, Section 315.32 was added to standardize the use and installation procedures for various MV equipment. The new Section now reads as follows:

315.32 Uses Permitted
(A) Type MV Cable
Type MV cable shall be permitted for use on power systems rated up to and including 35,000 volts, nominal, as follows:

1. In wet or dry locations.
2. In raceways.
3. In cable trays, where identified for the use, in accordance with 392.10, 392.20(B), (C), and (D), 392.22(C), 392.30(B)(1), 392.46, 392.56, and 392.60. Type MV cable that has an overall metallic sheath or armor, complies with the requirements for Type MC cable, and is identified as “MV or MC” shall be permitted to be installed in cable trays in accordance with 392.10(B)(2).
4. In messenger-supported wiring in accordance with Part II of Article 396.
5. As exposed runs in accordance with 305.3. Type MV cable that has an overall metallic sheath or armor, complies with the requirements for Type MC cable, and is identified as “MV or MC” shall be permitted to be installed as exposed runs of metal-clad cable in accordance with 305.3.
6. Corrosive conditions where exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the conductor or insulation shall be of a type suitable for the application.
7. Conductors in parallel in accordance with 310.10(G).
8. Type MV cable used where exposed to direct sunlight shall be identified for the use.
9. Direct buried in accordance with 315.36.

(B) Type MV Cable Joints and Terminations

Type MV cable joints and terminations shall be permitted for use on power systems rated up to and including 35,000 volts, nominal, as follows:

1. Type MV cable joints and terminations, used where exposed to direct sunlight, shall be identified for the use.
2. Direct buried.
3. Where used intermittently or continuously submerged in water at a depth not exceeding 7 m (23 ft) type MV cable joints and terminations shall be identified for the use.
4. The environmental operating temperature range shall be identified.
5. Where used in one or more of the following conditions Type MV cable joints and terminations shall be identified for the use
   1. Underground chambers
   2. Tunnels
   3. Conduits
   4. Manholes
   5. Vaults
6. Corrosive conditions where exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the joint or termination shall be of a type suitable for the application.
7. In cable trays, where identified for use, in accordance with 392.10, 392.20(B), (C) and (D), 392.22(C), 392.30(B)(1), 392.46, 392.56, and 392.60.