Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2
Problems of impact of electromagnetic high-power pulses generated at nuclear explosion or by means of special equipment intended specially for damage of electronic equipment, in particular, digital protective relays and automatic systems, along with ways of protection against these impacts are consi...
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irk-123456789-1435912018-11-07T01:23:06Z Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 Gurevich, V.L. Електричні машини та апарати Problems of impact of electromagnetic high-power pulses generated at nuclear explosion or by means of special equipment intended specially for damage of electronic equipment, in particular, digital protective relays and automatic systems, along with ways of protection against these impacts are considered. 2011 Article Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 / V.L. Gurevich // Електротехніка і електромеханіка. — 2011. — № 6. — С. 21-28. — Бібліогр.: 19 назв. — англ. 2074-272X http://dspace.nbuv.gov.ua/handle/123456789/143591 621.316.925 en Електротехніка і електромеханіка Інститут технічних проблем магнетизму НАН України |
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Електричні машини та апарати Електричні машини та апарати |
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Електричні машини та апарати Електричні машини та апарати Gurevich, V.L. Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 Електротехніка і електромеханіка |
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Problems of impact of electromagnetic high-power pulses generated at nuclear explosion or by means of special equipment intended specially for damage of electronic equipment, in particular, digital protective relays and automatic systems, along with ways of protection against these impacts are considered. |
| format |
Article |
| author |
Gurevich, V.L. |
| author_facet |
Gurevich, V.L. |
| author_sort |
Gurevich, V.L. |
| title |
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 |
| title_short |
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 |
| title_full |
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 |
| title_fullStr |
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 |
| title_full_unstemmed |
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 |
| title_sort |
stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. part 2 |
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Інститут технічних проблем магнетизму НАН України |
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2011 |
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Електричні машини та апарати |
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http://dspace.nbuv.gov.ua/handle/123456789/143591 |
| citation_txt |
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2 / V.L. Gurevich // Електротехніка і електромеханіка. — 2011. — № 6. — С. 21-28. — Бібліогр.: 19 назв. — англ. |
| series |
Електротехніка і електромеханіка |
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AT gurevichvl stabilityofmicroprocessorrelayprotectionandautomationsystemsagainstintentionaldestructiveelectromagneticimpactspart2 |
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2025-07-10T17:31:17Z |
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2025-07-10T17:31:17Z |
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1837282031333015552 |
| fulltext |
ISSN 2074-272X. . 2011. 6 21
621.316.925
The main mistake that people make is that they are more afraid of today's troubles
than of the troubles of tomorrow.
/Carl von Clausewitz/
V.I. Gurevich
STABILITY OF MICROPROCESSOR RELAY PROTECTION AND AUTOMATION
SYSTEMS AGAINST INTENTIONAL DESTRUCTIVE ELECTROMAGNETIC IMPACTS
PART 2
, -
,
, ,
.
Problems of impact of the electromagnetic high-power pulses generated at nuclear explosion or by means of the special equip-
ment, intended specially for damage of the electronic equipment, in particular digital protective relays and automatic systems, and
also ways of protection from these impacts are considered.
3. EXPOSURE OF MICROPROCESSOR-BASED
RELAY PROYECTION DEVICES TO INTENTIAL
DESTRUCTIVE ELECTROMAGNETIC IMPACTS
Various antenna arrangements, cable terminals,
power-supply system, currents induced in encasement and
emissions penetrating through windows and doors made
of non-conductive materials and air ducts are the primary
routes for penetration of EMP into the electronics. Cur-
rents induced by EMP in land and buried electric cables
extending for hundreds and thousands of kilometers may
reach thousands amperes and the voltage in open circuits
may reach millions of volts. Antenna leads with the length
of only several meters may have induced EMP currents of
several hundreds amperes. EMP penetrating through con-
struction elements made of dielectric materials (non-
shielded walls, windows, doors, etc.) may induce currents
of dozens of amperes in the interior wiring. Long over-
head power transmission lines absorbing emission from
large areas and delivering it directly to the inputs of high-
sensitivity electronics are particularly vulnerable. Trans-
formers which can be installed in this way (metering and
power) have little effect on this process due to significant
internal capacitance between primary and secondary
windings. Since low amperage circuits and radio-
electronic devices normally operate under very low volt-
ages and currents (up to several volts and several dozens
of milliamps) the amperage and voltage at the inputs must
be lowered by several digits in order to ensure reliable
protection against EMP. Amazingly, optical data trans-
mission systems, widely used in relay protection, are as
sensitive to EMP as MPDs. This refers to controllers con-
verting electrical signals to optical at one end of a fiber-
optical communication line (FOCL) and restoring them
from optical signals at the other end of FOCL. For exam-
ple, IEC standard compliance tests of electromagnetic
compatibility of multiplexer types FOCUS [35] showed
that this equipment is susceptible to faults and damage
even under standard influences. The SCADA system with
a high number of microprocessor detectors and initial
elements connected into computer network is also ex-
posed even to low EMP.
While the risk of high-altitude nuclear explosions as
sources of EMP aimed at destroying national power sys-
tem is hypothetical, the probability of using non-nuclear
EMP generators by terrorists to simultaneously destroy
the most important nodes of the local electric power sys-
tems is rather high at any moment.
Data transfer systems using broad-band protocols
are the most vulnerable to intentional electromagnetic
pulses ( 155, Fast Ethernet, Gigabit Ethernet, etc.).
This can be explained by insignificant differences be-
tween the power of the desired signal and the power of
the interference in the upper spectrum. Today, coaxial
cables are substituted with simple twisted-pair cables in
order to make cabling cheaper, but it makes the system
even more vulnerable. Even today, twisted-pair Ethernet
cables are used in relay protection and, according to
Smart Grid concept, this trend will be extended to all
power industry controls.
Discrete electronic elements are much more impervi-
ous to voltage surge and other harmful effects than chips
[36]. According to [37] 75 % out of all damages to micro-
processor devices result from voltage surge. Such voltage
surges with an amplitude from dozens of volts to several
kilovolts generated as the result of circuit switching or un-
der the electrostatic discharges are "lethal" for internal mi-
croelements of chips and processors. According to [37]
regular transistors (discrete element) can withstand up to 70
times higher voltages of electrostatic discharges than mem-
ory chips (EPROM) of microprocessor systems. Computer-
ized industrial equipment (including, but not limited to,
MPD) is especially exposed to EMP as it is generally built
on high-density MOS-devices, which are very sensitive to
high-voltage transition processes. The specific feature of
MOS-device is very low energy (several tens of volts)
needed to partially or totally destroy it.
There are three levels of semiconductor device deg-
radation under the powerful EMP: functional disorder,
persistent parameter change and catastrophic irreversible
failures. Irreversible failure of a semiconductor is mainly
caused by overheating or field breakdown. [38-40]. Dam-
ages to microchip or memory elements resulting from
tapped electromagnetic impact can be hidden [15]. Such
damages can’t be discovered by any tests and can appear
unexpectedly. Besides, such EMP tapped by protection
can cause random reversible failures resulting from spon-
22 ISSN 2074-272X. . 2011. 6
taneous changes of the memory element content: "soft-
failures" or "soft errors". Errors of this kind (reversible
and self-recovering malfunctions) were not previously
detected on electronics built on discrete semiconductor
elements or regular chips.
Recent developments in nanotechnologies have sig-
nificantly decreased the size of semiconductor elements
(units and fractions of micron), reduced thickness of
semiconducting and isolating materials, lowered actuating
voltage, increased operating speed, reduced electric ca-
pacity of individual memory cells and increased packing
density of elemental logic cells in the device. All this has
resulted in the sharp increase in the vulnerability of mem-
ory elements to electromagnetic pulses. The problem is
exacerbated by the steady trend of memory element ex-
pansion in the up-to-date microprocessor structures. Many
modern high-integrated chips of microprocessor devices
contain a rather large number of integral memory ele-
ments with totally uncontrolled working order. A sharp
increase in vulnerability to EMP is also observed in high-
speed logical elements, comparators, etc., that is in almost
all modern microelectronics.
The Faraday cage is known as a good protection
measure against EMP. Concrete-steel constructions con-
taining a grounded grid and protection relays are located
in metal cabinets and MPD are enclosed in metal cases:
not so much of a cage rather a Faraday "matryoshka" (a
matryoshka doll is a Russian nesting doll which is a set of
dolls of decreasing sizes placed one inside the
other).However, there is more than meets the eye. First of
all, high-frequency pulses freely penetrate the gaps in the
Faraday cage through any non-metallic inserts and open-
ings, glass windows and air ducts. Such partially attenu-
ated EMP effects can cause partial destruction of p-n-
transitions of semiconductor devices resulting in changes
of the parameters and "flickering" failures of the appara-
tus. Such failures require a lot of maintenance resources
and limit the certainty in the apparatus reliability. "Flick-
ering" failures sometimes are difficult to detect which
require repeated disablement of equipment with signifi-
cant operating time spent on damage diagnosis. This fac-
tor should also be considered in estimating the protection
of apparatus against electromagnetic attack as partial or
incomplete protection can cause additional problems.
Another known problem, the so called "delayed
EMP effect", is an extremely dangerous HEMP property.
This effect appears within the first minutes after a nuclear
or electromagnetic detonation. At this time, EMP pene-
trating into electric systems generates localized electro-
magnetic fields. During the attenuation of the fields, there
are sharp voltage changes that appear which propagate in
the form of waves over long distances from the source of
the initial EMP through the power lines. Thirdly, mile-
long external outbound cables and wires of the RP cabinet
and building deprive even the attenuation effect of RP
cabinets and building.
4. PROTECTION OF MPD AGAINST EMP:
PROBABLE LINES OF ATTACK ON THE PROBLEM
Ideal protection against EMP would be the full isola-
tion of electronics against the environment and covering
the building with a bulk thick-walled ferromagnetic
shield. At the same time, we must realize that, in practice,
such MPD protection is impossible.
Thus, in practice we have to use less reliable protec-
tion measures, such as conducting grids or conducting
coating films for windows, honeycomb metal structures of
air intake and air holes as well as special conductive lu-
brication and conductive rubber gaskets located on the
frames of doors and hatches.
Fig. 8. Control cabinet with upgraded protection against EMP
equipped with special loops, conductive rubber gasket, special
coupling and connecting elements, shielded air vent windows,
etc. (Equipto Electronics Corp.)
Today, there are special metal cabinets available on
the market that ensure significant attenuation of EMP.
Standard cabinets made of iron sheets having no windows
or gaps provide significant attenuation of EMP. Galva-
nized assembling panels of such cabinets, as well as spe-
cial conductive seals, significantly increase the effective-
ness of such cabinets since galvanizing allow equalizing
potentials within large areas (steel specific resistance is
0.103-0.204 Ohm mm2/m, and zinc specific resistance is
0.053-0.062 Ohm mm2/m). Aluminum has even lower
resistance (0.028 Ohm mm2/m). Thus some manufac-
turers produce single-block cabinets from a special alloy:
ALUZINC150 (Aluzinc® - registered trademark of Arce-
lor) – the material of which is 55 % is covered with alu-
minum, 43.4 % with zinc and 1.6 % with silicon. The
surface of the cabinet with this covering provides a high
deflection of EMP. These Cabinets are manufactured and
supplied to many countries by the Sarel company (today -
Schneider Electric Ltd., Great Britain). Similar cabinets
providing protection against EMP are also manufactured
by other companies, such as Canovate Group, R.F. Instal-
lations, Inc.; Universal Shielding Corp.; Eldon; Equipto
Electronics Corp.; ATOS; MFB; European EMC Products
Ltd; Amco Engineering; Addison, etc. This equipment
usually attenuates the emission per 80-90 dB on a fre-
quency of 100 kHz – 1 GHz.
Certainly, control cables must be shielded with
twisted-pair. The minimum requirement to the shield is
high density of armor (not less than 85 %).
Double-shielded cables have much a better shielding
effect, see Fig. 9. For relatively low frequencies (up to
several tens of MHz) the braided screen provides better
shielding than the foil mainly due to its thickness.
ISSN 2074-272X. . 2011. 6 23
Fig. 9. Double shielded cable. Left – with double braided screen;
right – with double combined shield (braided screen and foil)
Fig. 10. Dependence of shield factor from frequency
for braid-foil shields
However, the shielding properties of the braided
screen sharply decrease and become almost unacceptable
before the frequency reaches 100 MHz. At the same time,
the foil has flat AFR maintaining acceptable shielding
properties over a wide range of frequencies up to the GHz
range, see Fig. 10. Thus, cables with combined braid-foil
shield are the most preferable. Excellent protection
against EMP use cables combining pair-twisted wires, foil
shields for each pair of wires and three-layer common
shield made of foil, see Fig. 11.
Fig. 11. Cable RE-2X(ST)2Y(Z)Y PIMF characterized
as interference superstable (transmitting analogue and digital signals
up to 200 kbit/sec; pair-twisted wires, each pair shielded with PE
foil; three-layer common foil shield armored with steel wire;
external XLPE isolation; up to 24 pairs of wires per cable; can be
used outdoors and for burial; has high mechanical strength)
The Belden Company has developed and patented a
simple and effective method for shielding cables based on
foil-coated PE film (poly-sandwich) under the name of
Beldfoil®. The company produces cables with two layers
of foil and braid, or even four layers, where foil inter-
stratifies with braid two times combining best properties
of foil and braid in one cable, see Fig. 12.
Fig. 12. Multilayered shielding of poly-sandwich
developed by Belden
The effectiveness of cable shielding depends heavily
on the grounding effectiveness. As shown in [42], on the
one hand the grounding of control cable shield is effective
only against capacitive pickups (referred to as: electrostatic
protection) and doesn’t protect against inductive pickups
(interference reduction factor k = 1) since the shield doesn’t
provide a chain for closing the interference current.
If the shield is two-side grounded, there is an additional
chain (shield) with much lower impedance for high-
frequency signals than the ground. As a result the operating
signal is divided into two components: low-frequency com-
ponent goes through the ground and high-frequency goes
through cable shield. Therefore, for the high frequency com-
ponent the current in the shield is equal to the current in cen-
tral core directed in the opposite direction and is compen-
sated due to inductive coupling between shield and central
core. This provides protection against high-frequency pulses
emitted from the central core to the environment (to adjacent
cables) with an interference reduction factor k = 3-20. This
system is also effective under an external electromagnetic
pulse to the shield when the high-frequency signal induced
into the shield is bridged through the ground. When
connecting the shield to the ground bus, it should be
considered that a "wrapping" connecting wire on the shield is
unacceptable as well as coiling a long connecting wire
between shield and ground bus. Each additional loop
increases the impedance of the grounding on high
frequencies and significantly reduces its effectiveness. For
cabling at substations, laying a two-side grounded potential-
equalizing copper bus in parallel to the cable run can be an
additional solution capable of improving efficiency of the
shield. Its effect is provided by the fact that copper bus im-
pedance on high frequencies is much less than ground im-
pedance (and even shield impedance), so the main compo-
nent of the pulse interference high-frequency current will run
through the bus rather than through the shield.
While new cables with multilayered foil shielding
are capable of effectively attenuating external EMPs, old
types of cables with sparse braid do not satisfy these
needs. In order to attenuate an external electromagnetic
field these old cables can be laid in metal trays and tubes.
Plastic metalized trays widely used for laying control ca-
bles have the least shielding effect.
Due to a very thin conductive layer such a structure
operates effectively only on frequencies of 600 MHz and
above. On frequencies under 200 MHz it doesn’t work at
all [42]. At the same time, aluminum trays combined with
copper cable braid can attenuate induced voltages tenfold,
thus they can be widely used as effective EMP protection
measure. However, laying cables in steel water pipes en-
sure the best attenuation of induction over a wide range of
frequencies.
Prevention of EMP penetration into the apparatus
through different cable entries andconnections (plugs) is a
more difficult technical problem than cable shielding.
Today, there are a lot of special connectors with in-
tegrated EMP filters available on the market, see Fig. 13,
from many manufacturers, such as Amphenol; Spectrum
Control Inc., Spectrum Advanced Specialty Products;
EMP Connectors; ERNI Electronics; Sabritec; MPE; Gle-
nair Inc.; Captor Corp.; Lindgren-Rayproof, etc.
24 ISSN 2074-272X. . 2011. 6
Fig. 13. Several types of input connectors with integrated filters
manufactured by Spectrum Control Inc.
As a rule, such filters are manufactured based on fer-
rite rings or combined inductances and capacitances, see
Fig. 14, installed into the connector, see Fig. 15.
Fig. 14. Typical circuits of filters integrated into connectors
Fig. 15. Design of a connector with integrated filters by Glenair
Inc. High number of filtering elements are installed between two
plates
Filters, spark arresters, metal-oxide varistors and Zener
diode HS suppressants are widely used for protection of ca-
ble entries. The whole range of such devices is produced by
Company RFI Corporation and others, see Fig. 16.
Fig. 16. Cable entries filters manufactured by RFI Corporation
The range of filters manufactured by this company
includes filters for high currents (0.01 to 5000A) and volt-
ages (12 VDC to 5500 VAC).
Some manufacturers also produce power filters with
wide frequency characteristics which are especially designed
for protection against HEMP. Filters of the Captor Corp.
demonstrate excellent characteristics, see Fig. 17, and
EPCOS power filters, see Fig. 18, in the range of operating
currents up to 150 A (surge currents up to 12 kA) and a volt-
age of 440V. In such filters under the operating currents the
voltage drop reaches < 1 % per phase and attenuation
reaches 100 dB over a frequency range of 14kHz-40GHz.
EPCOS also manufactures cabinet-type, three-phase filters
working under the same frequency characteristics and oper-
ating currents of 1600 A, as well as low power multi-channel
filters for actuating and control circuits.
Fig. 17. Sealed power filters manufactured by Captor Corp.
designed for AC and DC power circuits up to 100A ensuring
effective EMP attenuation to not less than 100dB within the
frequency range of 14kHz-10GHz
Fig. 18. Dimensions and circuit diagram of three-phase EPCOS
filter (150 , 440 V)
ISSN 2074-272X. . 2011. 6 25
Many manufacturers offer excess-voltage suppressors
based on zinc-oxide varistors designed for 220/380/660V
circuits and allowing breakdown currents of up to 80kA.
Often, such devices contain in series, short-circuit protec-
tion fuses protecting the circuit in case of varistor damage,
and a blown-fuse indicator, see Fig. 18.
Fig. 19a. High-capacity protecting devices based on metal-oxide
varistors designed by Square D (Schneider Electric)
Fig. 19b. Powerful varistors of different types with rated voltage
of 130-1100 V and breakdown current of 3-100 kA
Metal-oxide varistors have high power but not
enough performance for protection against HEMP. Their
parameters decline under the repeated high-power im-
pulse loads. High-speed silicon Zener diode excess-
voltage suppressors do not have such disadvantages
(Transient Voltage Suppressor Diodes or TVS Diodes).
Their operation is based on a sharp drop of the resistance
from relatively high value to almost zero under induced
excessive voltage with a certain threshold, see Fig. 19.
Fig. 19c. Typical volt-amps diagram of zinc-oxide varistors
Besides, contrary to varistors, the parameters of such
excess-voltage suppressors do not decline under the re-
peated high-voltage effects and mode switch see Fig. 20.
Fig. 20. Volt-amps diagram of mono-directional (DC)
and bidirectional (AC) diode suppressors
Unfortunately, most modern supressors of this type
have limited pulse power (up to 1500W under voltages of
up to 600V) and are suitable for protecting electronics in-
puts but not for power and supply circuits. However, sev-
eral companies, such as Littelfuse, specialize in the devel-
opment and production of elements protecting against
surge voltage. Littelfuse, for example, manufactures sup-
pressors of much higher impulse power up to 30 kW and
discharge pulse currents up to several hundreds of amperes.
Varistros diode suppressors can be connected in-
parallel in order to increase discharge current. In-parallel
connection of different suppressors, such as varistors and
semiconducting suppressors, enables improving effi-
ciency of surge voltage protection, see Fig. 21. Such a
hybrid device demonstrates excellent characteristics: ini-
tial reaction is provided by fast-response suppressor 1
responding to pulse with an even steep leading edge and
absorbing a part of its energy; discharge current is limited
with resistors 2 preventing damage to suppressor.
Fig. 21. Hybrid protection device: 1 – semiconducting
suppressor; 2 – current-limiting resistor; 3 – powerful varistor
The voltage drop on resistors 2 increases the voltage
on varistor 3 resulting in sharp decrease in its resistance
and bridging resistors. The rest (the most part) of energy
is absorbed with a powerful varistor.
While designing means to protect against intensive
EMP, it should be considered that only one type of pro-
tection is not capable of ensuring effective overall protec-
tion. Thus, only the combination of all available protec-
tion means can provide complete protection.
One of such types of protection means is protection
of buildings and premises against EMP. The most effec-
tive protection is ensured with special panels combining
EMP-reflecting and absorbing layers, see Fig. 22.
26 ISSN 2074-272X. . 2011. 6
Fig. 22. Integrated protecting panel "Ferrilar-5"
However, fully shielded premises would cost a lot of
money. Therefore, in practice cheaper intermediate op-
tions including protective paints, films, curtains, hang-
ings, etc. can be used. Over recent years significant pro-
gress has been made in developing conductive paintings
and construction materials with unique properties and
wide application, as well as clear conductive coatings
which can be applied on the glass. Conductive paints,
lacquers and sprays based on copper, aluminum, brass,
nickel and graphite are manufactured by many companies,
such as Caswell, YSHIELD EMR-protection Company,
Less EMF Inc, Gold Touch, Inc., Spraylat Corp., Cyber-
shield, Applied Coating Technologies Ltd, BM Industria
Bergamasca Mobili S.p.A. High results shows protecting
paint Tikolak developed by Moscow company Tiko.
Tikolak is a new patented (in Russia) universal non-metal
conductive coating material combining carbon filling
compound with polymeric binding agent (8-20 % epoxy
plus graphite-soot compound with a mass ratio of
0.1:1.0:11-39 %, hardener 0.5-1.5 %, organic solvent,
etc). According to Tiko, this coating ensures shielding
against EMP over a wide frequency range up to 300 GHz.
Interior and exterior surfaces of a building coated with
Tikolak are characterized with manifestly less EMP pene-
trability. According to the manufacturer one layer of
Tikolak (only 70 micron) is able to reduce EMP intensity
by 3 – 3.5 times. This coating can be used on a variety of
construction materials, such as chip board, wood, gypsum
board, as well as with any flexible material, such as fab-
ric, leather, film, paper, etc. This coating can be covered
with any decorating material, such as wallpaper, paint,
ceramic tile, etc. and it costs much less than any foreign
analogues (about $70 per 1 kilo).
In order to get clear conductive glass reflecting EMP
the oxide films of such metals as tin, indium, zinc and oth-
ers are used. Production of such glass is very complex and
demanding while requiring costly equipment and qualified
staff. Tiko has developed and patented (patent RF
No.2112076) a high-tech and economic way of covering
the glass with conductive coating based on indium and
stannum oxides. Clear conductive glass is manufactured by
many companies, such as Tycon Technoglass, Pilkington,
Shenzhen Wanyelong Industry Co., Ltd, InkTec, etc.
The Alfapol Company in St. Petersburg has devel-
oped construction materials based on shungite, which is a
composite of solid carbon materials representing, in gen-
eral, amorphous carbons close to graphite. The chemical
composition of shungite is unstable: on the average it con-
tains 60-70 % of carbon and 30-40 % of soot. Soot con-
tains 35-50 % of silicon oxide, 10-25 % of aluminum ox-
ide, 4-6 % of potassium oxide, 1-5 % of sodium oxide,
1-4 % of titanium oxide and other compound materials.
Shungite combines the properties of regular construction
materials with rather high electrical conductivity. This
determines the ability to shield EMP [43]. According to
Alfapol, shungite composite radio shielding materials can
be divided in two classes by shielding method:
- Construction materials, including concrete,
bricks, brick mortar. These materials are capable of pro-
viding EMP energy attenuation at frequency ranges of
more than 100MHz at a level of not less than 100dB.
Their physical-mechanical characteristics match conven-
tional construction materials. Shungite materials were
tested in structures (concrete in slabs, bricks in blocking)
and proved to be compliant with the current requirements.
- Reconstruction materials, such as plasters and
pastes for converting conventional premises into shielded.
Layer of pastes (2-3 cm thick) provides shielding at level
of not less than 30dB at a range of more than 30MHz.
Plaster composite "Alfapol SHT-1" provides attenuation
of EMP per 10-15dB over a range of 10kHz-35GHz with
the thickness of plaster layer of 15mm. Conductive cur-
tains, fabric and floor coating of different manufacturers
can be used in addition to shungite walls, see Fig. 23.
Fig. 23. Conductive films, fiber and fabric attenuating EMP
(up to 80dB) manufactured by Koolon Fiber Tech. Corp.
4. IMPROVING DURABILITY OF MPD
In order to improve the durability of MPD both
technical improvements and organizational arrangements
are required, in our opinion.
Technical improvement is to equip each MPD with a
separate module containing special EMP filters (ferrite
rings, combination of different arresters, etc.). All ingoing
and outgoing MPD circuits should go through this module.
All manufacturers of MPD should be obliged to equip their
units with such modules. Such a module effectively matches
the current module structure of MPD [44], and it can be
replaced within the whole MPD lifecycle if new protection
technologies and filtering modules appear in the market.
This concept particularly includes implementation of stan-
dards for modular MPD construction and manufacturing
MPD as standard modular boards which can be combined in
RP cabinets with improved EMP protection [44].
Today, Russian experts have investigated improving
RP stability by implementation of two-level relay protec-
tion. B. D. Schedrikov proposes [45] effecting the first
level of relay protection with MPD and the second level
with a conventional electromechanical relay of type
-40 plus a time relay of type -12. Both sets of
ISSN 2074-272X. . 2011. 6 27
relays (MPD and electromechanical relay) are connected
in-parallel and the electromechanical relay actuation time
exceeds MPD actuation time by 0.1 second. Schedrikov
expects that that the electromechanical relay should spot
for MPD in case of malfunction under emergency mode
(in fact it operates under the logical OR function). It
should be noted that the in-parallel connection of MPD
and electromechanical relay is not something unknown
and has been practiced for a long time, see Fig. 24 [46].
Fig. 24. Distance protection of lines based on MPD type
MiCOM P437 (bottom) and on electromechanical type LZ-31
(top) connected in-parallel
However, such a connection scheme doesn’t elimi-
nate false responses of MPD under EMP, which can result
in at least as serious power network problems as malfunc-
tion. In his next article Schedrikov proposes changing
from an in-parallel connection of electromechanical relay
and MPD to the scheme where the electromechanical re-
lay of type KPB-126 permits actuation of a breaker trip
coil through microprocessor relay (using the logical AND
function). Surely, such actuation ensures improved relay
protection stability to false responses at HPEM, but re-
duces total relay protection reliability (it is the inevitable
consequence of improved sustainability to HPEM).
It is fair to say that we proposed to improve MPD sus-
tainability to powerful EMI with electromechanical relay
permitting MPD actuation in [47] 15 years before the pro-
posal of two level relay protection was published and we
suggested the idea about hybrid (mechanical-
semiconductor) relay protection device almost 20 years ago
[48]. Moreover, it was not an abstract idea, rather it was a
real design [49-51]. Today, thanks to the advent of a new
element base, such as miniature high-voltage reed switches,
reed switches for large switched currents, small-sized tran-
sistors and thyristors with an operating voltage of 1200-
1600V and switched currents of tens of amps, there are new
opportunities for the creation of hybrid relay (as a stand-
alone protecting relay, or as a starting unit for MPD).
In the publication [52], we attempted to demonstrate
the schematic of modern hybrid relays. In the electrome-
chanical part we recommended using reed switches.
Fig. 25. Fast speed over-current hybrid relay. 1 – module of
adjusted reed relay; 2 – slave reed relay in ferromagnetic shield;
3 – high-voltage thyristor; 4 – varistor
Their distinctive features are high reliability (if stan-
dardized current and voltage limits are observed), fast
response (fractions and units of milliseconds), excellent
dust and moisture protection, no stripping and regulating
during operation, small dimensions, full galvanic isolation
of control circuit (coil) from output circuit (contacts),
possibility to obtain high-voltage isolation between the
control circuit and the output circuit with very simple
means [53]. Another specific example of such hybrid pro-
tective relay is fast speed over-current relay which we
designed especially for separating network automation,
see Fig. 24 [54]. This device is very simple and contains a
minimum number of elements selected with high voltage
margin. Thus, for example the thyristor is designed for
1200 V and a miniature vacuum sealed switch is designed
for 2000 V. Isolation between input coil and reed switch
withstands voltages of 5 kV which can be increased if
necessary. A suppressor can be added connected in-
parallel to protecting varistor, as shown in Fig. 21.
As it follows from the above, recently new hazards
have appeared that encourage continuing to use electro-
mechanical protective relays resistant to powerful EMP.
Conversely, new types of electromechanical relays capa-
ble of ensuring backup protection should be developed
based on up-to-date technologies and materials.
Consequently, methods for improving MPD durabil-
ity shouldn’t include only technical innovations of the
MPD structure. Organizational arrangements should in-
clude the stocking of printed board sets (modules) for
MPD and proper storage. Since even disabled electronics
can be damaged, such printed boards for MPDs should be
stored in special well-shielded metal boxes. Modules of
the central processor should be fully operational without
28 ISSN 2074-272X. . 2011. 6
need of programming and set-up. Since it is not possible
to provide spare printed board sets for all MPDs used in
power systems for economic reasons, the most critical
MPDs of the power system should be determined in ad-
vance in order to have enough spare boards. For MPDs
having no spare boards, correct removal methods should
be considered. Substations and electric stations should
have complete and adjusted sets of protection panels
based on electromechanical relays which can be rapidly
put into operation in case of mass problems with MPDs.
In conclusion I'd like to note an oracular utterance of
Winston Churchill who said many years ago, that the lat-
est refinements of science are linked with the cruelties of
the Stone Age and to be amazed at his prophecy.
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Received 18.03.2011
Gurevich Vladimir, Ph. D., Honorable Professor
Central Electrical Laboratory of Israel Electric Corp.
POB 10, Haifa 31000, Israel
e-mail: vladimir.gurevich@gmx.net
Gurevich V.I.
Stability of microprocessor relay protection and automation
systems against intentional destructive electromagnetic
impacts. Part 2.
Problems of impact of electromagnetic high-power pulses
generated at nuclear explosion or by means of special equipment
intended specially for damage of electronic equipment, in
particular, digital protective relays and automatic systems, along
with ways of protection against these impacts are considered.
Key words – electronic equipment, relay protection,
electromagnetic impacts.
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