| |
DKTVA-EP
|
|
| DIGITAL DISTANCE PROTECTION
WITH AUTOMATIC RECLOSING EQUIPMENT FOR MEDIUM VOLTAGE NETWORKS |
| |
| The digital distance protection with automatic
reclosing equipment for medium voltage networks of type DKTVA-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.
|
| |
|
| |
| Application field |
| |
| The DKTVA-EP type digital distance protection
completed with sensitive earth fault protection and automatic fault locator
is applied as a selective phase and sensitive earth fault protection of
an overhead line or cable in a medium voltage network which is effectively
not earthed, but isolated or compensated and meshed.
A three shot three phase automatic reclosing equipment is also built
into the protection.
|
| |
| Main features |
| |
- electronic device with module system, controlled by microprocessors
set-up from IC's placed on plugged PCB's
- four stages each with impedance polygon characteristic
- the first three stages have forward direction, the 4th stage is directed
to backward
- the 1st and the 2nd stages measure by equation of Uline/Iline
as a classical measuring unit principle
- the 3rd and 4th impedance stages measure by equation of Uline/2*Uphase
as a classical starting unit principle
- impedance detection with three point measuring principle being insensitive
to CT saturation
- directional detection without dead zone on close-in-fault
- single earth fault detection as follows:
- sensitive zero sequence OC stage with independent timer (3Io>t)
- sensitive directional zero sequence OC stage (3Io>UoIoj t)
with operation condition of zero sequence voltage relay (Uo>)
- double earth fault selective detection with cyclic separation as follows:
- with distance protection
- high current zero sequence OC stage with independent timer (3Io>>t)
- instantaneous definitive trip on manual close-to-fault
- message appearing on LCD when protection operation
- three phase OC relay with independent timer, to be active on tripping
of VT midget CB only
- operation time is 25 ± 5 ms
- one fast reclosing cycle (FR)
- two slow reclosing cycles (1SR,2SR)
- accelerated or selective trip at first trip, after FR, after 1SR and
at definitive trip
- each reclosing cycle may be set to be active or blocked
- automatic recloser may be separately set to phase faults and to earth
faults
- two setting parameter packages may be pre-set to be easily possible
to change the automatic recloser working mode manually or by SCADA
- the device may be set to instantaneous Uo> trip during WUV (Work
Under Voltage)
- digital design with independent A/D converter, digital signal processor
(DSP) and separate main processor
- automatic fault locator displaying the last fault data
- built-in self check function with dc supply check, trip/close circuit
check and Watch Dog, with healthy-to-work failure signal and message
on LCD display
- external communication connectors for RS 232 on front plate, and for
optical fibre cable on back plate
- event log for storing 50 events, event sequence recorder with 1 ms
resolution for 300 events
- 16 optical coupler inputs
- 16 output relay contacts, 6 of which have fixed operation, 10 of which
may be freely programmed by matrix
- type changing (NO or NC) of last 10 relay contacts may be required
on ordering (NO's in factory)
- intelligent digital function matrix
- additional two timers (T1, T2) used in matrix
- the matrix rows are the relay functions, they may be programmed to
self-holding
- the matrix columns are the programmable output relay contacts
- handling protection (to set, to display messages, to inquire event
recorder data, etc.) by external PC, or by built-in man-machine connection
- on-line screen display may be seen on an external PC to be easy commissioning
and testing, to get real time current values
- real time clock handling with the aid of a RAM with battery, which
may be synchronised through an optical fibre cable by external PC or
through a digital optical coupler
|
| Working principles |
| |
| The current and voltage inputs go through inductive
auxiliary transformers and low pass filters to the multiplexer and the sample/hold
circuit which gets sample in each 0,5 ms. Signals of an A/D converter go
through high speed series bus to the central unit and to the fault recorder
if it was ordered as an option. On the PCB of central unit, a digital signal
processor (DSP) makes necessary arithmetical operations with high speed.
A central processor carries out the time delaying and logical functions,
and holds interconnections with the optical coupler inputs and the output
relay drivers.
The overcurrent stages (3Io>t, I>t) detect current with average
measurement. The operation conditions of the phase OC stage is that the
VT midget CB trips, i.e. when the impedance stages are also blocked.
The distance protection has got four directed impedance stages,. the
first three stages have forward direction, the 4th stage is directed to
backward
The four stages of the distance protection are blocked by the VT midget
CB trip.
All the four distance protection stages have polygon characteristics
in the impedance plane, see Figure 1.
Figure 1.
All the four impedance stages work with an algorithm solving the transmission
line differential equation.
The momentary values of six impedance measuring units of the protection
calculated may be read on an on-line screen of an external PC connected
to the protection. Checking the proper connection of analogue inputs is
helped by an on-line screen on which each analogue signal may be inquired.
The suitable directional connection of device may be also known, checked
by symmetrical load current.
The distance protection is able to receive permissive overreach and underreach
transfer trip command from the distance protection placed on the other
side of the protected line. The command overrides the second stage timer
[t(Z2<) = 0].
On close-in-fault, the protection remembers the voltage before the fault.
This feature gives a direction detection without dead zone.
On close-to-fault, the fact of whole voltage collapse (neither before
nor under the fault) determines the close-to-fault event, so if there
is current detection in the same time as well, the protection trips instantaneously
and definitely.
On an effectively not earthed network, the current value of a single
earth fault is fairly low compared to the phase fault current. The single
earth fault is catched by a sensitive directional zero sequence OC stage
(3Io>UoIoj t), which has an operation condition of zero sequence voltage
relay (Uo>) for safety.
On an effectively not earthed network, a double earth fault, i.e.single
earth faults in two different phases and two different places occurs very
frequently.
If double earth fault occurs in one line, the distance protection trips
it.
If the two earth faults occur on two different lines, the distance protection
system trips always the line on which the fault takes places before the
other in phase sequence (cyclic selection system).
Three shot three phase automatic reclosing equipment is built into the
device. Any possibility of the reclosing cycles may be separately blocked.
The reclaim time of the automatic recloser is set to teml = 5 s, fixed.
Operation of some output relay contacts, of the logical (dc) busbar protection
and of two additional timers (matrix column units) may be separately programmed
by software matrix.
Seven red LED's on the front plate give fast information about the events
on protection operation.
|
| |
| Technical data |
| |
| Rated secondary current, In |
1 A or 5 A |
| Rated secondary voltage (line), Un |
100 V or 200 V |
| Rated frequency |
50 Hz |
Overload capacity
voltage circuit, thermal, continuous
current circuit, thermal, continuous
1 s |
2×Un
4×In
100×In (if In = 1 A), 50×In (if In = 5 A) |
| Dynamic current limit |
100×In |
| Accuracy, impedance relays, (over 50 % In) |
± 5 % |
| Accuracy, current relays, (over 50 % In) |
± 2 % |
Accuracy, timers, with 10 ms steps
with 1 s steps |
± 3 ms
± 12 ms |
| Hysteresis, impedance stages |
15 % |
| Reset ratio, current relays |
95 % |
| Binary inputs (opto-coupled) |
16 pcs |
| Output relay contacts |
16 pcs |
Output contacts, electrical data:
rated switching voltage
continuous load current
making current
DC. breaking capability at 220 V,
at pure conductive load
at load of L/R =40 ms
optionally at load of L/R =40 ms |
250 V
8 A
16 A
0.25 A
0.14 A
4 A |
Auxiliary DC. voltage
voltage tolerance |
220 V or 110 V (the same supply unit)
88 to 310 V |
| Permissible ambient temperature |
0° to 50°C |
| Insulation test (IEC 255) |
2 kV, 50 Hz
5 kV, 1.2/50 ms |
| Disturbance test (IEC 255) |
2.5 kV, 1 MHz |
| Electrostatic discharge (ESD, IEC 801-2) |
8 kV |
| Burst test (IEC 801-4) |
2 kV |
| Electromagnetic radiation |
IEC 801-3 |
|
Setting ranges:
|
Impedance stages on real axis, R
on imaginary axis, X |
0 to 10000×(*10*Cu*Ci) mW
steps 10×(*10*Cu*Ci) mW
0 to 10000×(*10*Cu*Ci) mW
steps 10×(*10*Cu*Ci) mW |
Setting of directional relay,
angular coefficient on X axis, -R1/X1
angular coefficient on R axis, -X1/R1 |
0 to 50 %, steps 1 %
0 to 50 %, steps 1 % |
Line impedance for fault locator,
Xn (line)×(*10*Cu*Ci)
|
100 to 5000 mW,
steps 10 mW
|
| The factors found in above parameter equations: (*10*Cu*Ci)
=Un/10*In |
| CT primary rated current, In |
50 to 1500 A, steps 25 A |
Phase OC relay, I> / In
(operates on VT midget CB trip only) |
30 to 2500 %, steps 5 % |
Sensitive zero sequence OC stage,
3Io> /In |
10 to 104 %, steps 2 % |
High current zero sequence OC stage,
3Io>> /In |
50 to 2500 %, steps 5 % |
Zero sequence directional relay,
minimum angle, j(IoUo)min |
0 to 359°, steps 1° |
Zero sequence directional relay,
maximum angle, j(IoUo)max |
0 to 359°, steps 1° |
Zero sequ. directional relay, reset ratio
(hysteresis angle), j(IoUo)hyst |
0 to 359°, steps 1° |
Residual voltage relay, Uo>
/ Un
(zero sequence voltage relay) |
0 to 100 %, steps 1 % |
|
Separate timers:
|
| Impedance stage timers, t |
0 to 60000 ms, steps 10 ms |
| 1st additional timer, t[T1] |
0 to 60000 ms, steps 10 ms |
| 2nd additional timer, t[T2] |
0 to 600 s, steps 1 s |
| Phase OC timer, t[I>] |
0 to 60000 ms, steps 10 ms |
| Sensitive zero sequ. OC timer, t[3Io>] |
0 to 60000 ms, steps 10 ms |
| High set zero sequ. OC timer, t[3Io>>] |
0 to 60000 ms, steps 10 ms |
| Voltage stage timer, t[U>] |
0 to 60000 ms, steps 10 ms |
| Voltage stage reset timer at earth fault holding,
treset [U>] |
0 to 600 s, steps 1 s |
| FR dead time |
0 to 60000 ms, steps 10 ms |
| 1SR and 2SR dead time |
0 to 600 s, steps 1 s |
| Healthy-to-work failure signal timer |
0 to 600 s, steps 1 s |
| External communication type |
optical fibre cable or RS 232 |
| Optical fibre cable operation mode |
radial or loop |
| Series communication speed (BaudRate) |
150 to 19200 Baud, (with twice steps) |
| Daily automatic self-check time |
0 to 23 hour 59 min., steps 1 min. |
| Automatic self-check block |
setting to 60 min. |
| No. of substations within a system |
0 to 254 |
| No. of devices within a substation |
0 to 254 |
|
| |
| Design, size |
| |
| An EuroProt device is always rack mounting. It has two design
forms. One of the forms is suitable to mount into a standard 19" inch
cabinet frame, this form is also able to mount 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.
Outline size of a 19 inch cabinet frame mounted device and a panel mounted
device with flash mounted form is as follows.
|
|
Width
|
Height
|
Depth
|
|
483 mm
|
132,5 mm
|
201 mm
|
Outline size of a panel mounted device with raised-hinged form is as
follows.
|
Width
|
Height
|
Depth
|
|
490 mm
|
250 mm
|
250 mm
|
Weight 8 kg.
|
| |
| Options |
| |
Some especial units as built-in parts may be required to
be delivered with the distance protection as follows:
- digital fault recorder
- longitudinal differential protection
- SCADA connection
- relay contacts with 4 A breaking capability
- toroidal type CT input PCB
|
| |
| Data to be ordered |
| |
- Protection type [DKTVA-EP]
- Protection case type [19 inch cabinet frame mounted device, panel
mounted
- device with flash mounted form, panel mounted device with raised-hinged
form]
- Rated current [1 A, 5 A]
- Rated voltage [100 V, 200 V]
- Output relay contact types (if deviates from the Technical Data)
|
|
|