ENGR. MARITES R. PANGILINAN, P.E.E.

ENGR. MARITES R. PANGILINAN, P.E.E.

WHAT IS LOW VOLTAGE INSULATION COORDINATION AND WHY IT IS IMPORTANT WHERE DO SURGES COME FROM HOW DO SPDs WORK/TYPE OF SPDs SPD SPECIFICATIONS SPD COORDINATION /CASCADING COMPUTATIONS

WHAT IS LOW VOLTAGE INSULATION COORDINATION AND WHY IT IS IMPORTANT

What is Low Voltage Insulation Coordination? Insulation coordination aims at reducing the likelihood of equipment dielectric failure brought about by voltage surges popularly known problem called overvoltage, where equipment or a circuit is exposed to more voltage than it could handle.

It consists of matching the various surge levels that may appear on an electrical installation with the surge withstand of the industrial or domestic equipment within the system. Why is Low Voltage Insulation Coordination Important? This will ensure safety of people, protection of equipment, and, to a certain extent continuity of supply. To achieve this purpose, a surge protective device is added to an electrical system to aid in managing these voltage surges. ANSI/UL 1449 Third Edition ANSI/IEEE C62.41.1 (2002) IEC 61643-1

World Standards for Surge Protective Device 10-250kA Mode 20-500kA Phase 1449 3 rd ANSI/UL : Standard for transient Voltage IEEE C62.41.1 (2002): Guide On The Surge Environment In Low-Voltage (1000V And Less) AC Power Circuits 61643-11 IEC Lowvoltage surge protective devices Part 1: Surge protective devices connected to low-voltage power systems Requirements and tests. Type 1: 12,5-33kA per Pole Type 2: 8-65kA per Pole, Up to 160kA in China ccc

WHERE DO SURGES COME FROM

WAVEFORMS ARE USED TO TEST SURGE PROTECTIVE DEVICES Identifying the characteristic of the transient voltage surges will lead to the correct application of the SPD

Three Important Waveforms 1.Combination wave 8/20µs, 1.2/50µs 2.Ring wave 0.5 /10µs 3. IEC 10/350µs

WHERE DO SURGES COME FROM Two Basic Types of transient Voltage Surges ( IEEE C62.41 Standard): First, a combination-wave transient. A combination wave is associated with lightning-induced transients on utility power lines. The second waveform, called a ring wave. It is important in testing SPD s higherfrequency response to transients created within a facility by interrupted load currents. Closed Circuit Opening of Circuit Lightning Induced Transients (Combination Wave) Switching - Example : Switching of breaker (Ring wave)

WHERE DO SURGES COME FROM Combination Wave The combination-wave transients that could be expected from lightning were characterized, One waveform shown comprises the test CURRENT, and is defined by an 8 microsecond (written 8μs) rise time, with a 20μs trailoff. At that point, the wave has diminished to 50% of its peak value. The accompanying VOLTAGE waveform for lightning has a 1.2μs rise time with a 50μs trail-off. The test parameter just described is called a combination wave because the test source must provide both the current and voltage waveforms simultaneously.

Ring Wave A ring wave is an oscillatory surge with relatively high voltage levels at relatively high frequency, but with limited energy content. As shown, the ring wave is characterized as having a fast rise time of only 0.5μs along with a 10μs period, which yields a natural frequency of 100 khz. Ring waves are associated with: o fuses opening, o power factor/capacitor switching action, o load switching of motors, pumps, compressors, other electrical loads.

The IEC Class I test for SPDs According to IEC 61643-1 (2002) [B10], the test impulse current of the Class I test is defined by its peak value and charge transfer. A further stipulation is that the specified peak current and charge transfer be reached within 10 µs. Because these stresses are substantial, several levels of peak current values are tabulated in that IEC standard, allowing a case-by-case decision on selecting the appropriate level. The standard also states that a typical waveshape that can achieve these parameters is that of a unipolar impulse current. A proposed additional note states that one of the possible waveshapes meeting these parameters may be the 10/350 μs waveshape defined in the IEC documents dealing with lightning protection. DIRECT HIT

Three Important Waveforms 1.Combination wave 8/20µs, 1.2/50µs 2.Ring wave 0.5 /10µs 3. IEC 10/350µs

Impulse withstand category IMPULSE WITHSTAND CATEGORY (IEC) Example of equipment in category Required impulse withstand voltage I (low impulse voltage) II (normal impulse voltage) III (high impulse voltage) IV (very high impulse voltage) Sensitive electronic equipment connected to the fixed installation Domestic appliances and portable tools connected to fixed installations Equipment intended to be installed in a part of the fixed installation where a high degree of availability of overvoltages is expected, such as distribution boards, circuit breakers and wiring systems Equipment intended to be installed at or near the intake to the installation, such as the energy meter 1.5KV 2.5kV 4.0KV 6.0KV Required minimum withstand voltage for equipment where installation Rated voltage is 230V

IEEE 62.41 LOCATION CATEGORY Category C environments are located on the LINE side of the service disconnect. Outside and service entrance Service drop from pole to building Run between meter and panel Overhead line to detached building Underground line to well pump Category B environments are immediately adjacent on the LOAD side of the service disconnect breaker. Category B environments are characterized as having short branch circuits and feeder lines. Distribution panel devices Bus and feeder industrial plants Heavy appliance outlets with short connections to service entrance Lighting systems in large buildings Category A : Outlets and Long Branch Circuits --All outlets at more that 10 m (30 ft.) from Category B. --All outlets at more than 20 m (60 ft.) from Category C. Notice that Category C environments are subjected only to combination wave transients, Category B environments are tested using both ring waves an combination waves. Category A environments are tested with ring waves only.

Comparison between IEC and UL Surge Protective Devices Protection IEC Use linked to /based on risk assessment UL 3rd edition Use linked to /based on point of installation Line side Type1 Used to protect against the effects caused by direct or closeup strikes Type1 Used after service transformer but before the first circuit breaker Line /Load side Type2 Used to protect against the effects caused by remote strikes, inductive or capacitive coupling, and switching surge voltages Type2 Permanently connected SPDs after the circuit breaker (most of products) Load side Type 3 Used to protect particularly sensitive termination Type3 Cord Connected, Direct Plug-in Component - Type4 Used as discrete components

COMPARISON OF DIFFERENT STANDARDS ANSI/IEEE62.41 Category C Outside, service entrance equipment Category B Service equipment, Major feeders, and short branch circuits Category A Long branch circuits and receptacles 10KV or more 6KV 4 KV Classification of SPD (UL 1449 3 rd Edition) SPD Type 1 In=10kA, 20kA SPD Type 2 In=3kA, 5kA, 10kA, 20kA SPD Type 3 In= 3kA wave Combination wave (8 x 20 μs ) & (1.2 x 50 μs ) Combination wave / Ring wave Ring wave IEC 61643 TEST CLASS Class I (10 x 350 μs) Class II (8 x 20 μs ) Class III (0.5./10μs) Overvoltage Category Category IV Category III Category II Category I Overvoltage withstand 6KV 4KV 2.5KV 1.5KV Classification of SPD (IEC) SPD Type 1 SPD Type 2 SPD Type 3 Impulse discharge current (Iimp): maximal discharge current for impulse wave 10/350 S, which SPD can withstand at least 1 time. Maximum discharge current (Imax): maximal discharge current for impulse wave 8/20 S, which SPD can withstand at least 1 time. Open circuit voltage (Uoc): open circuit voltage of the combination wave generator at the point of connection of the device under test

HOW DOES SPD WORK/ TYPES OF SPDs

HOW DOES SPD WORKS? Connected in parallel to the incoming SPD has big impedance When the overvoltage comes, SPD conducts and drives the surge current to the earth For efficient protection of installation and equipment use SPD!

TECHNOLOGIES USED IN SPDs Spark Gap without trigger Triggered Spark Gap Gas discharge tube MOV Zener diode Type1 Type1 Type1 or 2 Type1 / 2 / 3 Type3 Discharge Capability Fast Response Due to high MOV current withstand capacity technology can be used in Type1 SPD Flashover happens in Spark gap used technology -> limited number of applications of use

SPD SPECIFICATIONS

IEC STANDARD COMPLIANT SPD UL/ANSI STANDARD COMPLIANT SPD available in 30kA, 60kA, 100kA and 150kA per phase peak surge capacity with 200kAIC short circuit current rating.

SPD SPECIFICATIONS Surge Protective Device Specifications 1. DEVICE CIRCUIT DESCRIPTION: This defines the components within the Surge Protective Device that actually suppress transient voltage surges. Examples include Metal Oxide Varistors (MOV s), gas-tube design. 2. MAXIMUM SURGE CURRENT: (I MAX ) This is the maximum discharge current for impulse wave 8/20 S, which SPD can withstand at least 1 time. 3. Nominal discharge current : (In) Crest Value of Surge current of 8/20 μs waveform associated with Type 2 spd s During the test SPD shall withstand this value ~20 times. 4. Impulse discharge current: (Iimp) Impulse current of 10/350 S waveform associated with Type 1 spd s and can withstand at least 1 time 5. Maximum continuous operating voltage: (Uc) Maximum r.m.s. voltage, which may be continuously applied to the SPD's mode of protection without it conducting the higher, the better 6.Voltage protection level : (Up) Maximum voltage to be expected at the SPD terminals due to an impulse stress In and or Iimp the lower the better (<1,5kV)

7. PROTECTION MODES: three modes of surge protection should be provided: line to neutral, ine to ground, and neutral to ground. Of course, clamping data should be furnished for each mode. In the case of panel-mounted units, especially those installed on delta systems or at service entrances where ground and neutral are bonded, the devices may provide adequate protection even though every possible suppression mode is not applicable. 8. SAFETY AGENCY APPROVALS: Certification organizations like UL, IEEE, IEC, CSA, and NOM, should be specified along with their appropriate test standards, product categories, and reference file numbers.

UL 1449 TYPE 1 The peak value of an 8/20 μs (Type 1 or) remains functional after 15 surges UL 1449 TYPE 2 Type 2 devices can be tested using a 3, 5, 10 or 20 ka.

SPD COORDINATION/ CASCADING

CASCADING Cascading is the term used to describe the method of combining several levels of surge protective devices into the one installation. This takes advantage of the best features of each device to improve the protection level for the equipment. Often manufacturer recommends using a high surge current capacity device to divert the bulk of the transient over-voltage at the origin of the installation. In the case of a Type 1 & 2 device this would be either the spark gap arrester or a high current capacity MOV. Should finer protection be required, the next step is to install a Type 3 device near the terminal equipment. Cascading increases the current diverting capacity of the SPD system whilst maintaining a low voltage (Up) to ensure the best protection for valuable equipment. Selecting SPD of the same manufacturer or make will ensure correct coordination between devices

FACILITY-WIDE PROTECTION SOLUTIONS IEEE EMERALD BOOK RECOMMENDS A CASCADE (OR 2-STAGE ) APPROACH

Type 1: when the building is fitted with a lightning protection system and located at the incoming end of the installation, it absorbs a very large quantity of energy; PROTECTION DISTRIBUTED LEVELS Type 2: absorbs residual overvoltages; Type 3: provides "fine" protection if necessary for the most sensitive equipmentlocated very close to the loads. Type1 Type2 Type3 MDB SDB FDB 90% 9% 1%

200kA IEC 62305-1. Maximum lightning current parameter for LPL 1 is fixed at 200kA 100kA 50% 100kA 50% Three phase TT, TNS, IT (with neutral) systems: 100kA /2 = 12.5kA/wire 4 wires Three phase TNC, IT (without neutral) systems: 100kA/2 =18.7 ka/wire 3 wires Single phase TT, TNC system: 100kA =50kA/wire 2wires

COMPUTATIONS

COMPUTATIONS V = L di/dt

COMPUTATION High-energy transients occur whenever a current is interrupted. The higher the current, the greater the amplitude of the transient. The following formula can be used to determine the transient voltage level (represented by V in the equation): V = L di/dt L - is the circuit s total inductance. di - represents the rate of change in the current. dt - is the interval of time over which the current changed. Note that since dt is the denominator in this fraction, the faster the transient (meaning the smaller the number represented by dt), the larger the transient amplitude (represented by V) becomes.

Example - Computation for Determining voltage protection level (U protec ) at at the Installation point of SPD Step 1 : Connections of a SPD to the loads should be as short as possible in order to reduce the value of the voltage protection level (installed Uprotec) on the terminals of the protected equipment. The total length of SPD connections to the network and the earth terminal block should not exceed 50cm. Step 2: The voltage U prot is the sum of protection level of the SPD U p and inductive voltage drop appearing on the conductors connecting SPD and protective device : Uprot = U p + U ind = U p + Ldi/dt U i The voltage sensed by the device U prot has to be less than dielectric strength: U prot U w The protection level of the SPD (kv) is determined as: U p = Uprot - U ind = Uprot - Ldi/dt U i

Step 3: To calculate using example above: a) Assuming that the total length of the conductor is L = L1 + L2+L3 = <50 cm b) The load to be protected is a sensitive load For the conductor A distributed inductance of a typical conductor is approximately 1μH/m, which at the current rate of rise of 1 ka/μs contributed approximately with 1kV per meter length. Hence applying Lenz s law to this connection: ΔU= L di/dt ΔU - the transient voltage level L - is the circuit s total inductance. di - represents the rate of change in the current dt - is the interval of time over which the current changed. The normalized 8/20 μs current wave, with a current amplitude of 8kA, accordingly creates voltage rise of 1000V/m of cable. ΔU=L di/dt = (0.5m) 1 x 10-6 x 8 x10 3 = 500V 8 x 10-6 For the voltage protection level The required protection level of SPD at termination board is determined as overvoltage category II which is 2.5 KV. Up (maximum voltage protection level) as per manufacturer brochure is 1.5kV. Hence Uprotec = U p + U 1 + U 2 = 1.5kV + 500V =2kV U prot U i Hence 2kv < 2.5kv The device is protected by the SPD

Example 2 - Coordination of surge protective device P1 P2 The fine-protection device P2 is installed in parallel with the incoming protection device P1. If the distance L is too small, at the incoming overvoltage, P2 with a protection level of U2 = 1500 V will operate before P1 with a level of U1 = 2000 V. P2 will not withstand an excessively high current. The protection devices must therefore be coordinated to ensure that P1 activates before P2. To do this, we shall experiment with the length L of the cable, i.e. the value of the self-inductance between the two protection devices. This self-inductance will block the current flow to P2 and cause a certain delay, which will force P1 to operate before P2. A metre of cable gives a self- inductance of approximately 1μH.

The rule ΔU= Ldi /dt causes a voltage drop of approximately 1000 V/m/kA, 8/20 μs wave. For L = 10 m, we get UL1 = UL2 1000 V. ΔU=L di/dt = (10m) 1 x 10-6 x 8 x10 3 = 1000V 8 x 10-6 To ensure that P2 operates with a level of protection of 1500 V requires U1 = UL1 + UL2 + U2 = 1000 + 1000 + 1500 V = 3500 V. ----> use 4kV impulse withstand Consequently, P1 operates before 2000 V and therefore protects P2.

THANK YOU!!!