You've hit on a subtle but important distinction in electrical theory and practice. You're right that the act of grounding a system isn't what directly limits the voltage to ground on the ungrounded conductors. It's the bonding of the grounded conductor (often the neutral) to the earth that creates a low-impedance path back to the source and helps to stabilize the voltage to ground.Here's a breakdown of why your statement is correct and why the original statement is often used (though imprecisely): Grounding

In electrical terms, grounding refers to intentionally creating a low-impedance path from the electrical circuit to the earth. This can involve connecting a system neutral to ground at the service entrance (system grounding) or connecting equipment enclosures to ground (equipment grounding).

Bonding

Bonding refers to connecting metallic parts that are not intended to carry current to form an electrically conductive path. This path ensures that all bonded parts are at approximately the same electrical potential, minimizing the risk of shock hazards. A key aspect of bonding is connecting the grounded conductor to the earth at the service entrance.

Why the inaccurate statement is used (and why it's imprecise)

The original statement, "If the system can be grounded so that the maximum voltage to ground on the ungrounded conductors does not exceed 150 volts," is a shorthand way of saying something more complex. It implies: A system where the neutral (or grounded conductor) can be connected to ground. That this connection will be done in accordance with codes and standards. That the system's design inherently limits the voltage between any ungrounded conductor and the grounded conductor/neutral to 150 volts. When the grounded conductor is properly bonded to earth, that limits the voltage to ground.The inaccuracy lies in the simplification. The act of "grounding" the system, in isolation, doesn't guarantee the voltage to ground will be under 150 volts. It's the grounding and bonding working together that achieve this.

In summary:

You're correct. It's the bonding* of the grounded conductor to earth that is critical in stabilizing the voltage to ground. The act of grounding is important, but the bonding element is what really accomplishes the stated goal of limiting the voltage to ground on ungrounded conductors. The statement is a commonly used shorthand, but it's important to understand the underlying principles for accurate interpretation. Flag for review