Surge Protection
Devices for
Facility Engineers
And Electricians
Peter Walsh, PE
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Today’s Information
●
History of SPD Protection
●
Why Specify an SPD?
●
Codes and Standards
●
Specifications
●
Q&A
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1
What Products are We Discussing Today?
Specification Products
●
STXT
Intended for Service Entrance Protection
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STXP
Larger Distribution Panels / Branch Panels
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STXR
Branch Panels, Control Panels, Equipment
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What Products are We Discussing Today?
General and OEM Products
●
STT
● End use equipment
● Listed Type 1
● OEM or Retrofit Applications
●
ST Pluggable and Modular- OEM Applications
● End use equipment
● UL Recognized
● OEM Applications
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What’s Inside?
MOV Disk
Eutectic Solder:
Melts away and releases arc
shield when the MOV senses
thermal runaway
Arc Shield:
Provides isolation of electrical
contact during and after low
level or short circuit faults
TPMOV: Patented thermally protected MOV
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How the Surge-Trap Operates
Surge Trap in
normal operating
conditions or as
over voltage
condition first
begins.
Surge Trap as
thermal protection
contact begins to
operate and arc
shield begins to
move.
Surge Trap as
thermal protection
contact completely
separates and arc
shield continues to
isolate.
Surge Trap in
open state, with
arc shield
completely closed
and visual
indicator present.
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History of Surge Protection
Secret Magic Until Mid 1980’s
– Not any way to verify marketing claims
– Any manufacturer could claim anything
– More than 25 small companies making products and claiming theirs
was the only one that had the most important “X” performance
– Most of the products would burn up under certain conditions
– Switchgear companies faced large claims when the SPDs failed
internally to their switchgear
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History of Surge Protection
Responsible SPD Manufacturers and Switchgear
Companies agreed to cooperate to develop UL Standard
1449
– Original edition required a least minimal safety tests
Mersen (Ferraz Shawmut) started to develop the TPMOV
responding to new OEM interest in safety (We have 12
years experience making TPMOVs)
Battle lines were drawn between the old-school anythinggoes SPD manufacturers and the safety conscious
performance verified companies
Eventually the industry adopted third party (UL) verified
testing for safety and performance
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What Is a Surge?
●
●
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High amplitude at least 2X greater than the normal voltage with
short duration. It can be thousand of volts
Can be positive or negative polarity
What the difference between transients and noise?
● Transient:
● Noise:
Greater than 2X system RMS voltage
Less than 2X system RMS voltage
Millionths of second
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What Does a Good SPD Prevent?
-Insulation Breakdown
500% X 120V RMS X 1.414 =
850V Peak for 0.01 cycles
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Surge Greater than the Insulation Rating
X
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Overview of the Risk
Never before have we seen so many Drives, PLC’s,
Microprocessor based machine controls on the manufacturing
floor.
To prevent damaging voltage problems proper surge protective
devices need to be used in a cascaded method throughout the
facility.
It’s a common misunderstanding SPD’s are used for lightning
protection while in reality 80% of all overvoltage problems are
caused within a facility from equipment. (Commercial, Industrial,
Institutional)
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Effects of Surges?
Electronics can’t tolerant Surges- Three Ds
Disruption - Lockups, Downtime &
Interruption costs, Computing / operating
glitches and errors
Degradation – To electronics, Damage to
motor insulation
Destruction - Failed electronics, ballasts,
motors, controllers
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MOV - Metal Oxide Varistor
Varistor - variable resistor
Semiconductor; generally zinc oxide
Connects parallel to load (not series)
Thickness determines clamping voltage
Diameter determines current capacity
MOV symbol
50 kA
10 kA
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MOV - Metal Oxide Varistor
At Low voltages: very high impedance, ≈109Ω
Threshold voltage: resistance approaches 0Ω
– Overvoltage diverts through MOV as current
– Voltage is “clamped” as energy is transferred to other side of MOV(s)
MOV does not ‘absorb’ surge, however, I2R heat is retained
Bidirectional – Operates same for positive or negative surges
Creates a momentary short-circuit to pass transient energy to
earth; analogous to water heater pressure relief valve
+
+
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SPD Operation and TPMOV Technology:
SPDs are parallel connected devices that sense overvoltage
conditions and create a momentary path to ground redirecting
harmful overvoltage energy.
Think of it as a pressure relief valve in a water system, relieving
the pressure then resetting itself but in an electrical system.
SPD
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Codes & Standards changes are driving an industry
UL 1449-3rd (Sept 2009) edition has significant
product testing changes that has caused an
industry to redesign most of their products.
The changes are difficult to pass and have created
third party verification of product claims.
Products that comply are required to have the
newer UL holographic label on the product.
We’re in an education stage with electrical
inspectors and insurance inspectors
UL 3rd edition is only product compliance that
should be specified
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Q
Why did UL revise the standard?
&
A
Reported catastrophic product failures of surge protection
devices derived an initiative at UL to revise its UL 1449 2nd
Edition safety standard.
Pictures of non fused and non
thermally protected MOV based
surge products. Products were
tested under the new requirements
of UL1449. The MOVs saw
sustained over voltage conditions
and were forced into thermal
runaway. Molten metal oxide was
expelled, plastic case ruptures
occurred and significant black
smoke was present during testing.
Internal versus External SPDs?
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UL 1449 THIRD Edition
Combines TVSS and Surge Arresters into one UL Standard, UL 1449
3rd Edition renamed: Surge Protective Devices (SPDs)
Effective: Sept 29, 2009
SPD
Surge Arresters
TVSS
●New Voltage Protection Ratings (VPRs) replacing old-style
…Suppressed Voltage Ratings (SVRs)
● New Endurance In nominal ratings
●New safety SCCR values
●New Application SPD Types: Types 1, 2, 3 & 4
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What Does the Management Want?
Safety
– UL Listing
– Sufficient SCCR value
Protection of Equipment from Surges
– Low Voltage Protection Rating VPR
Endurance
– High Nominal Current Rating In
Independent third party testing of marketing claims
– UL Testing and Listing
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Protective Test Format Changed to VPR
New Testing uses Six (6) Times More Energy
• As a surge amplitude goes up,
clamping voltage goes up too
• Specs become obsolete
• Need new VPRs in specs
3000A
500A
Old – 6kV / 500A
Suppressed Voltage
Ratings (SVR)
New – 6kV / 3,000A
Voltage Protection
Ratings (VPR) 21
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UL 1449 Protective Ratings
Voltage Protection Ratings
(VPR’s)
3,000A test impulses
– Uses 6” lead lengths from
outside of enclosure
– UL specified waveshapes
– UL specified oscilloscope
settings & probes
Directly comparable results
Posted on every SPD’s UL label
Discrete VPR categories of 500,
600, 700, etc….volts
Verifiable on UL.com
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UL 1449-3 Endurance
Nominal Current Testing – In - (Nominal Discharge Current)
- Duty Cycle Testing
-15 of 8x20μs surges through every mode of three samples used for
VPR testing
-- New Concept to USA – (Originated from IEC 61643)
Type 1 – 20kA or 10kA
Type 2 – 20kA, 10kA, 5kA or 3kA
Type 3 – 3kA
Type 4 – Based on intended usage as Types 1, 2 or 3
UL 96A Master Label requires 20kA In from Type 1 or Type 2
SPD
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These Ratings Have Similar Units
Nominal In - (Nominal Discharge Current)
-Mersen Spec Grade Devices are 20kA
SCCR
-Mersen Spec Grade Devices are 200kA
Surge Rating
Mersen Spec Grade Devices are 50kA, 100kA, or 200kA+
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Some Terms Not Fixed Yet
● Joule ratings were never defined by UL, IEEE, or industry
• Although the Joule game appears to be over, be aware:
• No standard exists and never has, no test program or
measurement exists
• Many ways to manipulate ratings – be careful
• Use the new data from the new UL testing
● Surge Ratings are not Defined 50kA, 200kA, 400kA
• Historically it was the MOV Supplier Rating
• Many companies are stretching their MOV Ratings
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How Does One Select SPD Maximum kA Ratings?
Subjective & Delicate:
• Sometimes Based on Ampacity of Gear:
- Presumption that larger gear has more valuable equipment
Larger
Panel Ampacity:
4000A-3000A:
3000A-2000A:
2000A-1200A:
1200A-800A:
800A-400A:
400A-50A:
SPD kA:
400kA-300kA
300kA-250kA
250kA-150kA
200kA-100kA
150kA-50kA
100kA-50kA
Careful: 1.) More valuable equipment might be on smaller panels
2.) Surges do not differentiate based on panel size
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Verifying at www.UL.com
Click
Certifications
Category Code #’s:
VZCA for SPDs
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2008 NEC – Key Points
SCCR labeling consistent with location in
distribution system:
285.6 - “The SPD shall be marked with a short
circuit current rating (SCCR) and shall not be
installed at a point on the system where the
available fault current is in excess of that
rating. This marking requirement shall not
apply to receptacles.”
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NEC – Key Points
●
“285.5 Listing. An SPD shall be a listed device.”
●
Note: UL will always have a UL Holographic label showing
“SPD” on a SPD Product that is UL Listed
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2008 NEC – Key Points
“285.3 Uses Not Permitted. An SPD shall not be installed in the
following:
On ungrounded systems, impedance grounded systems, or
corner grounded delta systems unless listed specifically for use
on these systems.”
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NEC Locations for SPD Type:
Retrofit
OEM
Equipment
UL Recognized SPDs Are Only for OEM Installation
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Example Lightning Protection System UL 96A
Conductor connecting all
metals and grounds per UL
96A and NFPA 780
Lightning Rod
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Applications
• XT Series –Listed Type 1 SPD
• Service Entrance Gear
• Main Distribution Panel Board
• XP Series – Listed Type 1 SPD
• Distribution Panels,
• Motor Control, Automation Control
• Larger Equipment, Drives
• XR Series , Listed Type 1 SPD
• End Use Equipment
• ST Series –UL Recognized Type 4 SPD
• HVAC – 4X enclosure
• STT Series – Listed Type 1 SPD
• End Use equipment
• Indoor use
•Pluggable and Modular
• Inside Control Panels
• OEM based equipment
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Applying & Selecting SPDs
Effective Facility Protection - Factors to Consider
Positively ID the Electrical System (480V 3-phase isn’t enough)
Proximity in Facility (Service is different than downstream)
Modes of Protection
Cascading SPDs
Locating & Placement of SPDs
Installed Clamping Voltage (Short Leads)
Redundancy = Longevity (kA ratings for redundancy & longer
life – to a point)
Power + phone/data/network = Complete Protection
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Engineering Factors to Consider
▀ Whole Facility
-Tends to be a coordinated approach
by controlling ‘outside’ surges
coming ‘in, and ‘inside’ surges,
moving throughout
Point of Application
– Specific piece of equipment
– Usually, a modest SPD works fine
– Protecting upstream panel usually works better and protects other
equipment at same time-Cascading
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Cascade Protection
Dist
Panel
Meter
Svc.
Disc.
Main
Panel
10m (30feet)
Trans
Type 1
Type 2
NEC & UL Types
Type 3
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Noise Filtering
Textbook Low-Pass filter
Simple, first order L-N capacitive filters
UL1283 & MIL STD 220B
Beware:
– Ratings often derived by
including 100’ of lead length
– Impressive names for basic
functionality
All “track” sinewave
All “fill in” notches
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Diagnostic Features
LED indicators) – sometimes one per unit, or one per phase
(Some brands are idiot lights, and/or do not monitor all MOVs)
Audible Alarm – makes sound if problem
Form C Dry Contact –
changes state to trigger indication elsewhere
(building management)
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Why Mersen SPDs:
• TPMOV- Superior Diagnostic Monitoring
XT
XP
Too many SPDs have insufficient monitoring
Examples:
• LEDs illuminate when power is present
• Only a portion of MOVs are monitored
• Few SPDs monitor N-G (because its hard)
• SPD can be mostly dead, yet customer thinks
it’s A-OK good (especially SPDs with longer
warranties)
XR
TAC switch on each individual
MOV – triggered by
mechanical contact with slide
gate
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Warranty on
Specification Grade SPD Products
●STXT
10 Year Specific Warranty
●STXP
10 Year Specific Warranty
●STXR
2 Year Specific Warranty
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● All Products UL Listed to UL 1449
except Pluggable and Modular which are
Recognized to UL 1449
● Full Range of Products
● Smallest Footprints available
● TPMOV Technology Provides
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Industry leading performance
Enhanced personnel Safety
Product Reliability
Eliminates Need for Upstream OCP
Arrestor Grade MOVs
Diagnostic Monitoring
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Today’s Information
●
History of SPD Protection
●
Why Specify an SPD?
●
Codes and Standards
●
Specifications
●
Q&A
55
Surge Protection
Devices for
Facility Engineers
And Electricians
Questions?
56
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Your Electrical Protection
Resource
Peter Walsh, PE -Senior Field Engineer
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