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For a gas tube arrester, a surge on either the tip or ring causes the arrester to short both the tip and ring to ground at the same time. The breakdown voltage from tip to ring is equal to the tip to ground voltage plus the ring to ground voltage.

For the solid state arrester, a surge on the tip only grounds the tip. A surge on the ring only grounds the ring. The balanced term is used to describe the breakdown voltage from tip to ring. For a balanced solid state arrester, the tip to ring breakdown voltage is equal to the ring voltage as well as the tip voltage. An unbalanced solid state arrester functions almost the same as the balanced arrester, except the tip to ring breakdown voltage is equal to the tip to ground voltage plus the ring to ground voltage.

The advantage of the balanced gas tube arrester is both the tip and ring are shorted to ground during a surge. This protects both lines during a surge. The balanced solid state device does not offer this protection. The advantage of a balanced solid state arrester is that the breakdown voltage from tip to ground, ring to ground, and tip to ring are equal. This provides better surge protection from tip to ring. This benefit is not available on the balanced gas tube arresters.

This is easier to understand from the diagrams below.

Balanced Gas Tube Arrester Equivalent Diagram (350 Volt - 3 Element Device) Before Surge
Before the surge occurs, the breakdown voltage from tip to ground or ring to ground is 350 Volts. The breakdown voltage from tip to ring is the sum, which is 700 Volts.

Balanced Gas Tube Arrester Equivalent Diagram (350 Volt - 3 Element Device) After Surge
After the surge occurs, the tube conducts (and becomes a short circuit to ground). The breakdown voltage from tip to ground or ring to ground becomes 0 Volts.

Un-Balanced Solid State Arrester Equivalent Diagram (300 Volt - 2 Element Device)
Before the surge occurs, the breakdown voltage from tip to ground or ring to ground is 300 Volts. The breakdown voltage from tip to ring is the sum, which is 600 Volts. When a surge is present on the tip, the left arrester will conduct to ground. The tip voltage will be limited to 300 Volts, regardless of the surge voltage. The right arrester is electrically isolated from the surge, so the ring remains at the same voltage it was before the surge. The un-balanced gas tube arrester uses two separate 2-element gas tubes, and functions identically to the unbalanced solid state arrester.

Balanced Solid State Arrester Equivalent Diagram (300 Volt - 3 Element Device)
Before the surge occurs, the breakdown voltages for all paths are 300 Volts. This is determined by summing each path (tip to ground, ring to ground, and tip to ring). When a surge is present on the tip, then the left arrester and the bottom arrester will conduct to ground. The tip voltage will be limited to 300 Volts, regardless of the surge voltage. The right arrester is electrically isolated from the surge, so the ring remains at the same voltage it was before the surge.

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