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TESTING OF IEC 61850-COMPATIBLE RELAY PROTECTION AND
AUTOMATION EQUIPMENT
Yu.L. Smirnov, N.M. Alexandrov
Scientific & Production Company “Dynamics”, Cheboksary, Russia
In 1990 a group of leading experts of the All-Union R&D Institute of Relay Construction
(Cheboksary) founded the Scientific & Production Company “Dynamics” (SPC Dynamics). At that
time the company’s founders were the leading developers of relay protection and automation devices
for 6-1150 kV power utilities.
Today SPC Dynamics is a major Russian developer and manufacturer of the state-of-the-art
testing facilities intended for testing of primary and secondary electric equipment, HF-equipment,
relay protection, emergency control and PLC.
Products of SPC Dynamics are the RETOM series instruments widely applicable in electric
power, oil and gas, energy-consuming enterprises and power supply utilities. Above 28 000 RETOM
devices are operating at about 4600 companies in Russia, CIS countries and abroad.
Long-term experience of development, application of global vendor components, continuous
and total quality control of the production process ensures high quality and reliability of RETOM
devices during 5 years.
Every month the leading specialists of SPC Dynamics deliver training courses and seminars in
a specially equipped training room. They also travel to customer sites, if required.
SPC Dynamics is a frequent participant of all-Russian and international exhibitions and
conferences, its products are appreciated and marked with awards and prizes.
The Company focuses on current trends of development and carries out R&D activities with
regard to IEC 61850 among others. Today this standard is a world top issue and an innovative trend
in the global power industry. This standard makes substations use brand-new data communication
means, the second revision of the standard («Communication networks and systems for power utility
automation») extends its application. Besides internal communication, this new revision supports data
exchange between substations, thus implementing the wide-area monitoring, protection and control
system WAMPAC. Nowadays, several pilot numerical substation projects are being carried out in
Russia to debug the IEC 61850-compatible HW/SW and to determine requirements to the equipment
installed.
The IEC 61850 standard covers logical signal communication (in the GOOSE-message
format) between IEDs and distribution of data received from primary signal detectors via the process
bus (part 9 (Sampled Values or SV)). This makes all LAN-connected IEDs receive data in real time.
Other benefits are reduced number of primary current and voltage transducers, improved
measurement accuracy and stability, and no more need in copper wires, i.e. reduced costs of
information network wiring and installation.
However, interaction of devices installed at the substation is a matter of concern. Their
compatibility must be the warranty of equipment manufacturers, but the end customer has to make
sure about it on his own to provide the reliable operation of its power system. Besides individual
relay protection and automation devices or IEDs, the whole system must be tested. Both methods of
data communication (GOOSE and SV) set high requirements to both – information network
performance and capacity. Complex testing is the mandatory project stage as loads will differ
depending on the number of IEDs, substation configuration and the information network.
According to regulations valid in Russia the tested device shall be disconnected from the
system before testing. When testing conventional protections, they are disconnected by means of
testing units.
Conventional testing of an IEC 61850-compatible IED assumes restriction of its impact on
primary switching units to avoid their maloperation (see figure 1), and tagging of test signals with the
«Test» flag. In this case the test results are displayed in either the testing equipment or the client PC
connected to the process bus, and the “Test” flag-tagged data is filtered. If maloperation of other
circuit breakers is expectable, the tested IED must be fully disconnected from the system and tested
in the stand-alone mode. The IED can be tested in the operating mode by applying signals not tagged
with the “Test” flag.
And here comes the question: what will happen to a relay protection and automation system,
if one of IEDs will be disconnected from it? The tested IED responds to signals obtained from other
system devices. At the same time, other IEDs may operate in response to messages obtained from the
tested IED or vice versa – issue an alarm or a tripping message when no data comes from the tested
IED. Besides, testing of an individual IED won’t be ‘a true-to-life story’. It makes the testing process
ideal as no load exists in the network and, hence, the amount of data available is not the same as in
real conditions. Therefore, disconnection of an IED from the information network for testing
purposes is undesirable.
Figure 1. Conventional IED testing configuration
IEC 61850 proposes not to take the tested IED out of service but to isolate it logically, i.e.
without disconnecting from the information network. The second revision of the standard manifests
new possibilities for such testing.
For this purpose the data object Behavior «Beh» is used according to its values «on», «test»,
«blocked», «test/blocked» and «off». Besides, the operating mode of nodes depends on that of the
logical unit as the latter monitors the nodes. The behavior («Behavior») of the logical unit depends on
its mode («Mod») and the node. The data object Behavior «Beh» is a read-only object. From the
testing point of view, most interesting are ON, TEST, TEST/BLOCKED modes:
«ON» – normal operating mode, the unit refuses any incoming data with the quality bit «q»
and the value «test»;
«TEST» - test mode of the IED logical unit. The application runs, commands with the quality
bit «q» and the value «test» are only received, all data objects sent to the network will also be tagged
with the “Test” flag;
«TEST/BLOCKED» - test/blocking mode of the IED logical unit. The application runs,
command with the quality bit «q» and the value «test» are only received. The tested node issues no
commands but can notify about the command, if issued. This is done to avoid CB maloperation.
Data attributes used in testing are now specified: "opRcvd" – received command; "opOk" –
processed command; "tOpOk" – time tag of command processing.
SPC Dynamics works on testing-related issues since the time when IEC 61850 was launched
and has developed RETOM-61850 - the device for testing the IEC 61850-compatible equipment. It
enables testing of secondary and primary equipment - instrument CTs and VTs (both optical and
conventional), bus connection units, circuit breakers, etc. - due to comprehensive support of IEC
61850 standard: receipt/transmission of GOOSE-messages and sampled values. The instrument is
intended for testing the commercial energy metering systems as it supports operation with the
sampling rate of 80 and 256 sampled values per period.
Figure 2 shows the testing procedure and operating modes of devices when IED is tested
without being disconnected. The tested device (DUT – Device Under Test) operates in «Test» mode,
the CB bay control IED - in «TEST/BLOCKED» mode.
Figure 2 – IED testing
Subsequent to change of the method of data acquisition from primary transducers their testing
procedure has also changed. To estimate the metrological performance of CTs and VTs, comparison
of primary analog values with the output digital data is required, being one of the most critical issues
today. Besides, it ensures evaluation of transient response, phase shift, distortions, noise, etc. (see
figure 3). For conventional transformers with the digital output it is possible to compare the output
analog signal with the output digital data flow. For the purpose of plotting the metrological
characteristics it is desirable to ensure the sampling rate of 256 (besides 80) samples per period
intended for the commercial energy metering system. The disturbance recorder estimates the delay in
generatiоn and passing of every data block and to make the conclusion about equipment operability.
The instruments designed and manufactured by SPC Dynamics can be used as analog signal sources
– the current source (max 3500 kA) and the voltage source (max 6 kV) in RETOM-21 and the current
source (max 30 kA) in RETOM-30KA.
Figure 3 – Primary equipment testing
Interoperability of analog and digital testing devices available at the substation is provided by the
bus connection units that convert analog magnitudes into the digital code (see figure 4). At that,
some relay protection and automation devices can operate with analog signals and others – with
sampled value flows.
Figure 4 – Testing of merging unit
During this test RETOM-61 – the instrument for testing relay protection and automation with
analog channels - is used for generation of analog currents and voltages for the equipment that
converts them into sampled values, and RETOM-61850 serves as a sampled value flow recorder. It
records and displays currents and voltages of sampled value flows accurately, including 256 samples
per period, thus, SV flow conversion accuracy can be defined. The figure shows the diagram used for
defining the amplitude error and estimation of conversion delays that lead to phase errors.
Synchronous remote analog and digital signal issue is also possible. Let us consider the example
of testing the phase comparison protection semi-assemblies installed at the line ends. One of them is
the old generation protection; another is compatible with IEC 61850. The objective is to test the
phase comparison element, the blocking angle and to record the phase characteristics.
Figure 5 – Testing of phase comparison protection (one semi-assembly – old generation, another –
IEC 61850-compatible)
Synchronization of test signal sources is a very important point in such tests. RETOM-61 can be
used as the analog signal source and RETOM-61850 – as the sampled value source. Synchronization
can be performed with the help of RET-GPS – an SPC Dynamics series-manufactured unit.
To setup and to check the measuring elements the manual source control mode is recommended.
PPS signals are connected to relevant RETOM inputs at each end of the line for synchronization
purposes. The complex testing may be carried out in the COMTRADE-format alarm generation mode
with external triggering on the set astronomical time.
The complex testing procedure (see figure 6) characterized by a huge amount of incoming and
outgoing signals has become less complicated due to Ethernet technologies. The testing equipment
simulates current and voltage SV flows in steady-state and fault transient conditions. GOOSEmessages are being processed simultaneously. Outgoing messages control the IED operation logic,
and incoming messages - the condition of IEDs and their interaction logic. Connection and testing
with one testing device are easier to perform, though it is still possible to connect several testing
devices into the general information network. An important test is simulation of real data flows
during line faults, when the IED condition changes many times and a large number of intermediate
logical signals and tripping signals is issued. The critical point of this test is evaluation of signal
transmission/receipt time and operation stability of the whole system. Another important test is check
of operation stability in conditions of a communication line failure when IEDs switch to the standby
channel.
Figure 6 – Complex testing
To carry out the above-mentioned tests one can use RETOM-61850 – an SPC Dynamics
developed and manufactured device that provides:
 receipt/transmission of 256 GOOSE-messages with 96 logical signals in each;
 receipt/transmission of max. 10 SV-flows with 80 or 256 samples per period;
 time synchronization via SNTP(NTP), PPS, PTP (versions 1 and 2), GPS;
 generation of “Test” flag-tagged commands for testing the equipment operating in the general
substation network. “Test” flag- filtering of received commands ensures selective only-test-signal
operation;
 GOOSE-messaging and SV-flow via one or two busbars, thus enabling simultaneous operation
with process and station busbars (to test the standby communication channel operation, use
additional redundant communication channels that support switching to standby channels). For
this purpose five configurable Ethernet ports are available in the device that can be assigned to
operation in different networks;
 recording of incoming GOOSE-messages, currents and voltages in SV-format with possible
estimation of time delays (built-in display of disturbance recordings with real time tags for
estimation of delays and deviations).
 IED operation simulation mode that supports connection of testing devices to the general network
for IED operation simulation during its local testing;
 Storm and peak load test mode of communication channels with simultaneous recording of
GOOSE-messages and SV- flows to estimate the system operability in fault conditions.
RETOM-61850 can be used either individually or together with optional devices:
RETOM-61(51) testing device, RET-64/32 unit, several RETOM-61850 devices in one general
network or other similar equipment.
Figure 7– RETOM-61850 device
Own instantaneous-operating binary inputs and outputs are used for:
 connection of an external timer for time measurement redundancy;
 connection of other testing devices, e.g., RETOM-21 or RETOM-30KA testing systems, for
synchronous generation of high analog current values;
 generation of logic commands and analysis of the response at common binary inputs/outputs.
Connection to RETOM-61(51) and RET-64/32 helps to extend the number of binary I/O for
testing the equipment, including IEC 61850-incompatible IEDs, by reversing GOOSE-messages to
binary I/O and back. In this case operation of IEC 61850-compatible IEDs can be tested together with
other IEDs.
RETOM-61(51) can be used in combination with RETOM-61850 for applying currents and
voltages to conventional IED analog windings; RETOM-61(51) analog I/O – for measuring currents
and voltages on conventional transformer windings. In such configuration RETOM-61850 can be
used for estimation of tested equipment operability via GOOSE-messages and display of binary input
currents and voltages of transformers and merging units.
Hence, complex testing of IEC 61850-compatible IEDs requires special testing devices, relevant
testing procedures and regulatory documents. Only then it is reliable to obtain the true data required
for making the final conclusion on feasibility of the given IED configuration, the network equipment
and the whole substation.