ZORC

Motor / Transformer / GeneratorSwitching Surge Protection Device

OVERVIEW PRESENTATION: HIGH LEVEL PRESENTATION: APPLICATION

Insulation Failure Costs

• Cost of removing failed equipment from service, and for reinstallation after repair.

• Cost of transportation to and from the site.

• Direct repair cost.

• Cost of downtime and lost production (or disruption to production).

Scope of Operation

• Spike description

– Amplitude 1-6 pu

– Rise time .1-.2µ sec

• Range

– Voltage: 400V to 40 kV

– Line Frequency: 50 – 60 Hz

50 - 60 Hz

ZORC

Air circuit breaker closed

Air circuit breaker Open

Air circuit breaker Open

Normal operation

Switching off motor

Zorc clamping the spike

Clamping of Switching Surges

Transient effects on cables

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ZnO (>2.1 p.u)

R C Earth

Single phase

Live terminal

Three phase units separate or in one tank

Internal connections

Benefits of ZORC

• ZORC halves the magnitude of steep wave-front surges impinging on the load terminals by providing a matched cable terminating impedance under transient conditions, thereby eliminating refraction of steep wave-front surges (i.e. eliminates voltage doubling effects).

• ZORC eliminates multiple pre-striking and re-striking transients associated with vacuum and other switchgear, by eliminating reflections of the pre-strike and re-strike current wave-fronts, and thus preventing high frequency current zeros in contact gap of the switch.

• ZORC provides a suitably low absolute limit to the magnitude of steep wave-fronted surges that may impinge on the load terminals, and slopes that portion of the steep wave-front which exceeds this limit.

• ZORC provides comprehensive insulation co-ordination, at all practical steep wave-front surge magnitudes and rise-times, within the motor impulse withstand levels recommended by the IEEE and CIGRë curves

Benefits of ZORC – Cont.

• ZORC protects new motors and dry-type transformers throughout their service life by reducing the magnitude, rise-time and frequency of occurrence of steep wave-fronts impinging on the load terminals.

• ZORC extends the life of motor and dry-type transformer insulation if retro-fitted to existing motors in service.

• ZORC saves money by eliminating losses incurred as a result of insulation failures of motors and dry-type transformers, in terms of both direct repair costs as well as costs of down-time leading to lost or disrupted production.

Product Features

CompactZORC is compact enough to be fitted within most motor/transformer terminal enclosures or switchgear panels.

Low CostZORC offers an unparalleled price/performance ratio.

Easy to applyZORC suppressors may be selected from a catalog with no detailed engineering required.

Motor/transformer mounting and switchgear panel Mounting versionsZORC versions are available for both motor/ transformer mounting (M type) and panel mounting (P type)

Single phase and three phase versionsZORC suppressors are available as both single phase or three phase versions. Single phase versions are suitable for installing in phase segregated terminal enclosures.

Product Features

Class 1 Division 2 Certification (ExN, non sparking)As an option ZORC surge suppressors may be ordered certified for use in potentially flammable atmospheres (Class 1 Division 2 locations), temperature classes T1 to T5, to SABS 970-1971 (amended).

Easy to installZORC suppressors may be mounted in any orientation, and convenient mounting brackets or clamps are provided. (See dimension drawings).

Well provenMany thousands of ZORC surge suppressors have been installed over the past 10 years, on motors, generators and transformers, solving the pressing problem of insulation failures and attendant repair and downtime costs.

Industries

ZORC suppressors have been installed in large quantities in the following industries:

• chemical• petrochemical• underground mining (gold, platinum, coal, other)• surface mining (coal, copper, uranium, iron ore, other)• metal beneficiation (steel, stainless steel, gold, platinum,

copper and uranium refineries)• power generation (generators, power station auxiliaries)• pumping (water pumping stations, oil pipelines)

Typical Applications

ZORC suppressors are applied in the following specific applications on motors, generators, and dry and oil immersed transformers and associated switchgear:

• Fans• pumps• Compressors• mills• crushers• refrigeration machines• motor-generator sets• mine winders• conveyors• underground and surface mini-substations and mobile substations• generators• power station auxiliaries• arc furnaces• induction furnaces

ZORC Pictures

Installation

• At motor• At panel• Compact version

• Any orientation clearance consideration• 2,5mm² flexible lead• 16 – 25mm² earthing• Surge arrestors where required• Watch vibration and water ingress

Testing

Visual inspection:

• No bulging of tank;

• bushings ok ? ;

• Check for oil leaks.

• Capacitance between bushings and earth : 0.1µ to 0.2µ Farad.

• No partial discharges are measured.

DC over potential test

• 28kVdc for 3/6 kV

• 47kVdc for 11kV

Comparison to other Methods

• Surge arrestors

• Surge Capacitors

Aggravating FactorsOptimised insulation and surge suppression

co-ordination covering various devices in use

Notes: (1) Normally fitted with parallel metal oxide power arresters.

(2) Clamping voltage: peak-to-peak = 2 x peak-to-earth volts.

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Metal oxide arrester (2)

Motor with-stand level (Cigrë)

Zorc at panel

Wave sloping capacitor (1)

Surge rise-time in microseconds

Zorc at motor terminals

Switch-onStalled trip

Unsuppressed switching surges

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k-to

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lts

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itch

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tri p

ZORC

The End ...

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