Grounding for 250V DC Control Systems

[Foringerj]

I work for an electric utility and recently encountered a large customer using a 250VDC system(two 125VDC Battery banks in series) for control and relaying on their switchgear. They intentionally grounded the center leg of this three wire battery system. We are using a tap of one of the 125VDC banks for control and relaying of the transmission equipment in this customer substation. We normally leave our 125VDC battery banks ungrounded and check for grounds using a ground detector. My question to the forum is this: Does the NEC require an intentional ground on 250VDC battery systems?

 

[infinity]

VIII. Direct-Current Systems
250.160 General.
Direct-current systems shall comply with Part VIII and other sections of Article 250 not specifically intended for ac systems.
250.162 Direct-Current Circuits and Systems to Be Grounded.
Direct-current circuits and systems shall be grounded as provided for in 250.162(A) and (B).
(A) Two-Wire, Direct-Current Systems. A 2-wire, dc system supplying premises wiring and operating at greater than 50 volts but not greater than 300 volts shall be grounded.
Exception No. 1: A system equipped with a ground detector and supplying only industrial equipment in limited areas shall not be required to be grounded.
Exception No. 2: A rectifier-derived dc system supplied from an ac system complying with 250.20 shall not be required to be grounded.
Exception No. 3: Direct-current fire alarm circuits having a maximum current of 0.030 amperes as specified in Article 760, Part III, shall not be required to be grounded.
(B) Three-Wire, Direct-Current Systems. The neutral conductor of all 3-wire, dc systems supplying premises wiring shall be grounded.

Look at 250.162(B) above: