The MAIN JOURNAL for POWER GRID SPECIALISTS in RUSSIA
2014
DIGEST, February, 2014
32
Digital substations
Digital sensor high-voltage test (35 kV).
A
few years ago the terms “smart grid” or “digi-
tal substation” could be used only by young
enthusiastic specialists as something very far.
But interest in smart grid inevitably
grew, pro-active research, testing and development were
carried out, and today the Government has made several
strategic documents determining energy development in
Russia. “Policy objective will be creation of intelligent
electric grid complex with active-adaptive power system
— new generation customer-oriented network based on
the multi-agent control principle on the basis of mass
balanced implementation of modern technological tools
and solutions in the complex”, as set out in “Development
Strategy of the of electric grid complex.” Thus, all
the approved government documents directly refer us
to creation of "Smart grids" in Russia, where digital
substation are the key part.
In correspondence with IEC 61850 «Communication
Networks and Systems in Substations» a digital substation
has three levels:
•
process
level;
•
bay
level;
•
station
level.
The station and bay levels are the most widely covered
and elaborated by Russian and foreign enterprises.
These levels are responsible for control, monitoring,
storing and distribution of data. Process level is not
paid so much attention to, although it is responsible for
collection of primary analog and discrete data, that is,
Process level development strategies
Dmitry UKRAINSKIY (Дмитрий УКРАИНСКИЙ), Leading Engineer,
Alexander ZHUKOV (Александр ЖУКОВ), Director General,
TERMA-ENERGO LLC leading engineer
primary information. This includes current and voltage,
presence or absence of voltage, busbars and transformer
temperature, cables insulation resistance and other
signals. Some of the most important decisions are made
basing on this information, so it must not be forgotten
that modernization and development of sensors collecting
primary information in substations is very important.
Our company has secured its place in the market
and established itself as a manufacturer and supplier of
quality components for power industry, such as voltage
detectors, voltage arc protection devices equipped with
f iber-optical sensors, voltage dividers, and others.
Also, our company develops and manufactures various
products for 6—35 kV electrical equipment using epoxy
compounds (post and entrance insulators, busbars). To do
this TERMA-ENERGO LLC uses latest 3D technology
for insulator and injection moulds design as well as
modern equipment and technological processes acquired
from the world leaders in this field, such as Hübers,
Vogel, Hedrich, Huntsman. This combination allows
TERMA-ENERGO to maintain high product consumer-
grade.
Development of modern element base and the adop-
tion of new international standards provided a good op-
portunity for our developers to use innovative approaches
to gathering primary information necessary to create ad-
vanced digital substations. Based on the existing problems
in the world experience in running the digital stations, a
clear understanding and concept to establish a harmonized
set of devices for collecting primary information has been
generated. Today it is one of the priority directions of
TERMA-ENERGO activity. This primarily concerns ac-
quisition of current and voltage data for commercial ac-
counting and protection.
Contrary to popular belief about the preferential use of
digital optical transformer at the substation process level
we should not forget that such transformers are most ap-
propriate and effective at high and extra high voltages.
While at medium and low voltages due to their high cost
and low sensitivity these transformers are not effective.
On the base of lengthy research our company has been
successful in developing high accuracy current and voltage
sensors outputting digital optical signals of currents and
voltages measured in real time. Workable specimens were
obtained and test results proved their effectiveness.
Current sensor consists of a specially designed high-
precision, high-speed and jam-protected analog-to-
www.eepr.ru
33
digital conversion board and original
measuring elements. All of this is placed
on high potential side, does not require
insulation and additional power source.
Thus, only an extra strong dielectric
fiber optic cable with two optical fibers
providing galvanic isolation is routed
to low potential side.
The first fiber transmits billing cur-
rent values of 0.2s accuracy [1] / 256
samples/cycle; the second fiber trans-
mits 10p accuracy [1] current data /80
(90) samples/cycle for relay protection
units.
The current output signal ratio for
relay protection device is 8000% of rated primary current.
Operating temperature range is -40° to +85° C. The rated
primary current is up to 5000 A.
Overall dimensions and weight of the current sensor is
relatively small and can be commensurate with the classic
measuring current transformer for 0.66 kV voltage. There-
fore, mechanical strengthening of high-voltage bus to in-
stall the sensor is not required. Dimensions and weight al-
most do not change under the increase of the rated current
within 10—110 kV voltage class. As for the cost of the
current sensor, it is a sequence lower in comparison with
cost of transformer based on optical laws and commensu-
rate with cost of classical measuring current transformers
starting from 10 kV voltage class.
Currently voltage sensor has an accuracy of 1%, and
operates within -25 º — +50 º C temperature range. This
sensor features a smaller dimensions and lower cost com-
pared to existing measuring voltage transformers, it has
no DC magnetizing and resonance phenomena inherent to
classical voltage transformers. Work is underway to in-
crease the accuracy of the sensor to class 0.2 [2] for use in
commercial accounting of electric circuits. Digital output
is similar to the output of current sensor.
To work on IEC 61850 standard these current and
vol-tage sensors require digital Merging Unit, capable of
receiving input digital optical signals and form a group
digital stream protocol per IEC 61859-9-2LE standard.
Using only digital signals, the accuracy of the informa-
tion received is maintained as digital optical signal car-
rying information from the transformer is not affected by
electromagnetic interference and, in addition, there is no
analog-to-digital conversion, which inevitably introduces
additional error. Moreover, lack of an analog-to-digital
conversion greatly simplifies Merging Unit and reduces
the dimensions.
In accordance with policy we seek to identify and work
through the most weaknesses and continuously engaged
in the development of sensors to collect other valuable in-
formation except for current and voltage. The next device
to be launched into serial production will be a tool for on-
line measurement of insulation resistance of cable lines.
Due to constant connection of the device to high voltage,
the time available for the measurement of this parameter
takes about 5 minutes as opposed to the currently existing
devices that perform the same task. The output signal may
support GOOSE-messages.
Feasibility studies undertaken suggest that the cost of
our equipment during the transition to serial production
will not exceed the cost of conventional solutions and will
provide a number of technical advantages:
•
improving measurement accuracy and information
transfer reliability;
• simplicity of design, operation and maintenance;
• unified platform data exchange (IEC 61850);
• high noise immunity;
• high fire explosion and ecological compatibility;
• digital signal in real time;
• absence of saturation and ferroresonance;
• small size and weight of the primary equipment;
• reduction in the number of copper cable connections,
number of devices, as well as more compact arrange-
ment.
So, due to the advent of IEC 61850 standard unified
data exchange platform made a reality transfer of
information using innovative devices, including digital
current and voltage transformers. However, a number
of questions remains to be solved and full integration of
these technologies providing smooth operation needs a
joint effort of manufacturers and developers operating in
the field of digital substations. Our company is open for
cooperation.
LITERATURE:
1. GOST 7746-2001 “Current transformers. General
specifications”
2. GOST 1983-2001 “Voltage transformers. General
specifications”.
Ltd, Bldg 3, Dudko str., Saint-Petersburg, 192029
Tel. +7 812-640-11-28, +7 812-346-50-09
http://terma-energo.ru
Оригинал статьи: Process level development strategies
A few years ago the terms “smart grid” or “digital substation” could be used only by young enthusiastic specialists as something very far. But interest in smart grid inevitably grew, pro-active research, testing and development were carried out, and today the Government has made several strategic documents determining energy development in Russia.
