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DCVA-EP, DCVA-DTVA-EP
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| DIGITAL PHASE SELECTIVE PROTECTION FOR RADIAL
LINE END |
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| The digital phase selective protection and
automatic recloser for radial line end of type DCVA-EP, DCVA-DTVA-EP is
part of device family named EuroProt. This short description contains special
data of this type. General and common features of EuroProt family can be
found in the EuroProt system information sheet. Accordingly it is proposed
to study both this short description and system information sheet too, in
order to understand the device entirely. |
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| Application field |
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The DCV A-EP digital protection is designed
for application on solidly grounded netwprks at consumer transformers, fed
by radial line or at "T" connected line end. The task of DCVA-EP
protection is to disconnect the appropriate phase of the transformer circuit
breaker at the radial or "T" connected line end, in case of single
phase to ground fault. This should happen at the same time as or after the
single phase interruption at the sending end of the line. Following the
successful reclosing at the sending end it recloses automatically the circuit
breaker after the set dead time.
Concerning the dimensions, structure and connections of the device version
DCVA-DTVA, it is identical with that of the DTVA-EP type digital distance
protection. If the network is extended, and the concerned substation with
radial topology is becoming part of the mashed network, the protection needs
only software upgrading, and without further
secondary changes in the bay, the device can be operated as distance protection. |
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| Main features |
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Overcurrent function:
- two zero sequence overcurrent stages (Io>>, Io>) with fix
and definite time delay
Overvoltage/undervoltage stage:
- three-phase function with phase selective operation
Software characteristics:
- built-in self check functions
- digital event recorder for 50 event, event sequence recording with
I ms time resolution for max. 300 events
- analog event recorder for short-circuit current and voltage data
- intelligent digital function matrix
Hardware characteristics:
- fully numerical type, with individual A/D converters, digital signal
processors (DSP) and separate main processor (DCVA-DTVA-EP version)
- 8 opto-coupler inputs
- 16 output contacts
- type of output contacts (NC, NO) can be selected when ordering
Communication:
- relay setting with 2x16 character LCD display, suitable also for text
messages and for event log display
- on-line screen of auxiliary PC for support of commissioning
- auxiliary communication connection selectable for RS 232 or fibre
optic cable
- optional SCADA connection with IEC 870 protocol
- parameters can be saved and saved parameters can be downloaded again
- real-time clock with battery-fed RAM (which can be synchronised via
fibre-optic connection by auxiliary PC, by the SCADA system, or via
opto-coupler digital input)
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| Principle of operation |
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The DCVA-EP device is a fully microprocessor
based construction, the functions and their versions are realised basically
on software.
The device contains more 87C196 type 16 bit micro-controller and a DSP performing
digital signal processing. The program is stored in EPROM, the message text
for the display is stored in EPROM as well. The parameter setting is loaded
in EEPROM. Events are recorded in battery supplied RAM.
The man-machine interface consists of a keyboard with six push-buttons,
above it the two row, 2x16 character LCD display, seven LEDs and two SW
pushbuttons. With auxiliary PC and with the handling program a device can
easier be operated.
The analog current and voltage inputs are connected via inductive internal
measuring transformers and low-pass filters to the multiplexer then to the
A/D converter, where all current and voltage signals are sampled in every
0,5 ms. The sampled values of the 16 bit A/D converter are passed via high
speed CAN bus to the digital signal processors (DSP), which perform arithmetic
operation with high speed. The outputs of the DSP are the processed and
evaluated measurements, as "started" signals of the relay functions,
which are sent to the CPU. The timers and logic functions are performed
here. The central processor communicates via parallel bus with the opto-coupler
inputs and with the relay drivers.
The protection measures the 120 kV voltage and current of the transformer.
The evaluated current is the zero sequence 3Io current at the 120 kV side,
the evaluated voltages are Ur, Us, Ut at the 120 kV side.
As In case of single phase to ground fault on the line the transformer supplies
zero sequence current, the starting element of the short-circuit protection
function is the two stage zero sequence overcurrent protection, according
to parameter setting. The low set overcurrent stage detects all kinds of
single phase to ground fault located on the whole length of the line, and
because of selectivity reasons, it has a time delay to be set by parameters.
The high set overcurrent stage has to operate only in case of ground faults
on the protected line. To over-bridge the switching transients, it has a
short, fix 100 ms time delay. The selection of the faulty phase is made
by undervolatge relays in each phese, set by parameters.
The protection at the line end must operate only in case of single phase
ground faults, for this reason the programming of the function assures,
that it will not operate in case two or three phase voltage dips.
The protection based on the 120 kV side Ur , Us and Ut voltages operates
not only by undervoltage function, but based on other parameters as overvoltage
protection as well, the measured values of which are necessary for automatic
reclosing. In case of single phase fault the protection selects the faulty
phase, and issues a single phase trip command with or without time delay,
then an automatic reclosing is initiated. The time delay measurement for
the dead time is started either if the voltage recovers to the healthy three
phase value, or at the moment of the CB trip, according to the logic parameter
set. After the trip of the circuit breaker ("CB" closed status
signals) two time counting is started at the same time (tEVA and tLVA timers).
The protection recloses the circuit breaker if the voltage is healthy either
after expiry of the tEVA counter or when tLV A timer is running, and the
voltage is healthy in all the three phases. In this way the three phase
healthy operation is recovered, and the protection resets without external
interaction.
If during the tLVA timer runtime the three phase voltage does not recover,
or if the fault occurs again, then automatic reclosing function stops, and
a definitive single phase trip state remains until the interaction of the
operator.
The software delivered with DCVA-120/EP digital phase selective line protection
and automatic recloser allows reading on-line information characteristic
to the momentary state of the protection, and request and displaying digital
events, and setting of the function parameters.
On-line information:
- 120kV side 10 current in A and Ur , Us, Ut phase voltages in kV, operation
and drop off of functions, display of three phase healthy voltages
- state of the signals received on opto-coupler inputs
- counting of single phase trip commands, automatic reclosing, and definitive
trip commands
- service display to check and test the device
The digital event recorder stores the following events:
- DCVA enabling
- DCVA local enabling
- voltage dependent single remote enabling
- remote disabling
- Ut undervoltage
- definitive trip
- Io>> operated
- Io> operated
- phase reclosing, R phase trip, CB failure, acknowledgement, S phase
trip, self-check disturbance
- Ur undervolatge, T phase trip, Us undervolatge, automatic reclosing
Beside the digital events the protection stores events evaluated in graphical
form, the signals of which are as follows: Io>> and Io> operation,
Ur, Us, Ut undervolatge, DCVA trip, automatic reclosing, definitive trip
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| Technical data |
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Rated secondary current, In
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1 A or 5 A |
| Rated secondary voltage (line), Un |
100 V |
| Rated frequency |
50 Hz
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Overload capacity, thermal
voltage circuit, continuous
current circuit, continuous
1 s |
2xUn/Ö3
4xIn
100xIn (In=1 A), 50xIn (In=5 A) |
| Dynamic current limit |
100xIn |
Accuracy, voltage relays (above 50% Un
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current relays (above 50% In)
timers |
± 2%
± 2%
± 3 ms (steps 10 ms)
± 12 ms (steps 1 s) |
| Reset ratio, current relays |
95% |
Number of output relays
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12 kom |
| Type of contacts (NO / NC) |
1 NC, 11 NO (or as requested) |
Output contacts ratings:
rated switching voltage
continuous load current
switching on current
breaking current at 220 V dc,
pure conductive circuit
L/R = 40 ms load
option at load of L/R = 40 ms |
250 V
8 A
16 A
0,25 A
0,14 A
4 A |
Auxiliary DC voltage (the same supply unit)
voltage tolerance |
220 V or 110 V
88 V to 310 V |
| Permissive ambient temperature |
0o to 50o C |
| Insulation test (IEC 255) |
2 kV, 50 Hz
5 kV, 1.2/50 µs |
| Disturbance test (IEC 255) |
2.5 kV, 1 MHz |
| Electrostatic discharge (ESD; IEC 801-2) |
8 kV |
| Burst test, (IEC 801-4) |
2 kV |
| Setting ranges |
| Low set overcurrent function Io>/In(AV) |
10-1000%, step 10% |
| High set overcurrent function Io>>/In(AV) |
10-1000%, step 10% |
| CT rated primary current, In(AV) |
100-1250 A, step 50 A |
| Phase selective undervoltage function |
10-100%, step 1% |
| Overvoltage function |
10-100%, step 1% |
| CT rated primary voltage |
10-250 kV, step 1 kV |
| Time delay, overcurrent function Io> |
100-5000 ms, step 100 ms |
| tEVA single phase short reclosing dead time |
100-6000 ms, step 100 ms |
| tLVA single phase dead time |
10-100 s, step 1 s |
| Logic parametar: voltage dependent APU |
1=yes, 0=no |
| Helathy to work failure signal timer, t(fail) |
2 s, fixed |
| External communication type |
RS 232/fibre optical cable |
| Optical cable operation mode |
Radial or loop |
| External communication speed (BaudRate) |
150 to 19200, step 2x |
| Daily automatic self-check time minutes |
0 to 23 h 59 min, step 1 min |
| Automatic self-check block |
to 60 min |
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| Design, size |
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An EuroProt device is always rack mounted, it
has two design forms. One of the form is suitable to be mounted into standard
19" cabinet frame, this form is also suitable to be mounted directly
to a relay panel with flash mounted form. The other form is a relay panel
mounted device with raised-hinged form. Its size depends on the chosen form.
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Design
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Width
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Height
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Depth
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Rack mounting
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483 mm
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132,5 mm
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201 mm
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Panel mounting
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490 mm
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250 mm
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250 mm
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Weight: 8 kg.
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| Options |
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- digital disturbance recorder (see separate information sheet)
- SCADA connection (see EuroProt system information sheet)
- output relays with 4 A breaking capability
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| Information required with order |
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- Protection type [DCVA-120/EP or DCVA-DTVA-EP]
- Rated current [1 A, 5 A]
- Rated voltage [100 V, 200 V]
- Output relay contact type [NC or NO]
- Protection case type
- Options if needed
- Needed trip circuit supervision
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