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1.Which standards to follow for low voltage Surge Protective Devices?
Globally people use different standards to choose low voltage Surge Protective Device.
There are below main standards,
Surge Arresters for Low-Voltage installations:
IEC 61643-11 (International)
EN 61643-11 (Europe)
VDE 0675-6-11 (Germany)
NF/EN 61643-11(France)
UL1449 (USA)
Surge Arresters for photovoltaic installations:
IEC61643-31
EN 50539-11
UL1449 DC PV SPD
Surge Protectors for Telecom equipment:
IEC 61643-21 (International)
ITU-T recommendations K11, K12, K17, K20, K21, K36 (International)
UL 497 A/B (USA)
Among the above standards,IEC61643-11 and UL1449 are most widely used forlow voltage SPD for AC application,IEC61643-31 and UL1449 DC PV SPD are used for DC PV SPD.
For telecom / dataline surge protectors,IEC 61643-21 and UL 497 A/B are widely used.
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2.SPD category per IEC61643 (EN61643)
Class I SPD tests: Tests carried out with the impulse discharge current Iimp, with an 8/20 current impulse with a crest value equal to the crest value of Iimp, and with a 1,2/50 voltage impulse
Class II SPD tests: Tests carried out with the nominal discharge current In, and the 1,2/50 voltage impulse
Class III SPD tests: Tests carried out with the 1,2/50 voltage - 8/20 current combination wave generator
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3.SPD category per UL1449
Type 1: Permanently connected SPDs intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt- hour meter socket enclosures and Molded Case SPDs intended to be installed without an external overcurrent protective device. Type 1 SPDs for use in PV systems can be connected between the PV array and the main service disconnect.
Note: SPDs investigated for Type 1 applications are automatically suitable for Type 2 applications and may be marked for SPD Type 1 and/ or Type 2 applications. SPDs only marked "SPD Type 2" are not suitable for Type 1 applications.
Type 2: Permanently connected SPDs intended for installation on the load side of the service equipment overcurrent device; including SPDs located at the branch panel and Molded Case SPDs.
Type 3: Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example cord connected, direct plug-in, receptacle type and SPDs installed at the utilization equipment being protected. The distance (10 meters) is exclusive of conductors provided with or used to attach SPDs.
Type 4 Component Assemblies: Component assembly consisting of one or more Type 5 components together with a disconnect (integral or external) or a means of complying with the limited current tests.
Type 1, 2, 3 Component Assemblies: Consists of a Type 4 component assembly with internal or external short circuit protection.
Type 5: Discrete component surge suppressors, such as MOVs that may be mounted on a PWB, connected by its leads or provided within an enclosure with mounting means and wiring terminations.
Note: Type 5 SPDs and Types 1, 2, 3 and 4 component assemblies are intended only for factory installation within another component, device or product.
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4.What is SPD's protection mode?
Mode of Protection to SPD means an intended current path, between terminals that contains protective components, e.g. line-to line, line-to-earth, line-to-neutral, neutral-to- earth.
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5.What does SPD's Thermal Stability mean?
SPD is thermally stable if, after heating up during the operating duty test, its temperature decreases with time while energized at specified maximum continuous operating voltage and at specified ambient temperature conditions.
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6.Short-Circuit Current Rating per IEC 61643 and UL1449
In IEC61643, Isc means maximum prospective short-circuit current from the power system for which the SPD, in conjunction with the disconnector specified, is rated.
While in UL 1449, Isccr, the suitability of an SPD for use on an AC power circuit that is capable of delivering not more than a declared rms symmetrical current at a declared voltage during a short circuit condition.
SCCR is not the same as AIC (Amp Interrupting Capacity).SCCR is the amount of“available” current that the SPD can be subjected to and safely disconnect from the power source under short circuit conditions. The amount of current “interrupted by the SPD is typically significantly less than the“available”current.
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7.What is Voltage Protection Rating (VPR) per UL 1449?
A rating selected from a list of preferred values as given in the latest revision of ANSI/UL 1449. The value of VPR is determined as a higher value taken from table of UL 1449 to the average measured limiting voltage determined during the first set of measured limiting voltages tests during the transient-voltage surge suppression test using the combination wave generator at a setting of 6kV, 3kA. As a standardized rating system, VPR allows the direct comparison between like SPDs (i.e. same Type and Voltage).
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8.Temporary Overvoltage Value of the Power System
Power frequency overvoltage occurring on the network at a given location, of relatively long duration. TOVs may be caused by faults inside the LV system (UTOV(LV)) or inside the HV system (UTOV(HV)).
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9.What is UL 1283 EMI/RFI Filtering?
UL 1449 Listed SPDs include filter circuits that have been evaluated as a UL 1283 (Standard for Electromagnetic Interference Filters) filter. These are complimentary UL Listed as a UL 1283 filter and a UL 1449 SPD.
By definition and the scope of UL 1283, UL 1283 Listed filters are evaluated for load-side applications only, not line-side applications. Consequently, UL will not complimentary list a Type 1 SPD as a UL 1283 Listed filter. However, a Type 1 SPD might include a UL 1283 filter as a Recognized Component within a Listed Type 1 SPD, which has been fully evaluated for line-side usage. Manufacturers of such products generally offer the identical SPD as a Type 2 UL 1449 Listed SPD with complimentary Listing as a UL 1283 Listed filter.
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