Grounding for transient suppression. In order for the transient suppression to operate properly and
provide optimum equipment protection, the ground side of the transient suppressor must be connected as
directly as possible to ground. The ground for the high-energy level suppressor must be connected directly to
the nearest J-Box wall.
Suppressor installation. Suppressors can be installed between applicable terminal boards and the
ground with short direct connections. Maintaining short lead lengths is important to prevent inductance of long
lead lengths from delaying turn-on and response of the transient suppressors.
18.104.22.168.23 Types of Available Transient Suppressors. Three different types of suppressors are available to
provide transient protection as listed below. Operating characteristics for each type are provided in subsequent
paragraphs, followed by desirable operating characteristics.
Zinc oxide nonlinear resistor (ZNR) or metal oxide varistor (MOV).
Silicon avalanche diode suppressor (SAS).
Gas-filled spark gap.
Operating Characteristics of Transient Suppressors.
Characteristics of ZNR-type suppressors.
Response time: 50 nanoseconds or less, any risetime.
Clamping voltage: 225% of breakdown voltage maximum for surge currents projected.
Breakdown voltage: 22 V dc to 1800 V dc at 1 milliampere.
Standoff voltage: 14 V dc to 1599 V dc.
Variable, depends on amplitude of surge current, satisfactory for 10-year
Characteristics of SAS-type suppressors.
Response time: 1 nanosecond or less, any risetime.
Clamping voltage: 165% of breakdown voltage maximum at rated peak pulse current.
Breakdown voltage: 6.8 V dc to 200 V dc at 1 milliampere.
Standoff voltage: 5.5 V dc to 200 V dc.