DTVA-EP

DIGITAL DISTANCE PROTECTION WITH AUTOMATIC RECLOSING DEVICE

The digital distance protection with automatic reclosing device, type 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.

Application field

The DTVA-EP type digital distance protection completed with one and three phase three shot automatic reclosing device and automatic fault locator may be applied as a selective phase and earth fault protection and automatic reclosing device of an overhead line or a cable in a high voltage effectively earthed meshed network.

Main features

electronic device with module system,controlled by microprocessors set-up from IC's placed on plugged PCB's
five stages with impedance polygon characteristics
4th and 5th stage may be set to forward and backward direction
stages measure by equation of U_L / I_L at three phase and phase-to-phase faults, and by U_F / (I_F + a3I₀) at phase to earth faults
impedance detection with three point measuring principle which is insensitive to CT saturation
directional detection without dead zone on close-in-fault
instantaneous definitive trip on manual close-to-fault
three phase overcurrent relay with independent time delaying, it may be set with PROTLOG operation equation to be active on tripping of VT midget CB only
sensitive earth fault overcurrent protection with zero sequence current detection
one and three phase automatic recloser (OR, TR)
one fast reclosing cycle (FR)
two slow reclosing cycles (1SR, 2SR)
step acceleration [t(Z2<) = 0]
step acceleration or selective trip at first trip, after FR, after 1 SR and at definitive trip
step acceleration may be blocked on three phase trip
each reclosing cycle may be set to OR or TR
each reclosing cycle may be set to be active or blocked
automatic fault locator displaying the last fault data
operation time is 25 ± 5 ms
digital design with independent A/D converter, separate digital signal processor (DSP) and separate main processor
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 on front plate for RS 232, on back plate for optical fibre cable
event log for storing 50 events, event sequence recorder with 1ms resolution for 300 events
16 optical coupler inputs
20 output contacts, 8 of which have fixed operation, 12 of which may be freely programmed by matrix
type of last 12 contacts may be required on ordering (NO or NC)
intelligent digital function matrix
operation equations of PROTLOG system to be freely chosen with 18 outputs and 32 inputs
5 equations of which is matrix row, i.e. to operate contacts, handling (to set protection, 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 principle

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 NO converter go through high speed series bus to the central unit and to the fault recorder if it was ordered as an option. In the 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 may be chosen by programming of the relevant PROTLOG equations. It is advisable to programmed a condition the phase OC stage can operate only if the midget VT CB trips, since then the impedance stages are blocked. The phase OC stage blocks the automatic reclosing, trips always definitely but in one or three phases according to the setting of definite trip parameter.
The distance protection has got three stages with forward direction and two stages with forward as well as backward direction arbitrary settable. The first stage does not have time delaying, but time delaying of the others may be set independently.
The five stages of the distance protection are blocked by the VT midget CB trip.
The first and second stages of the distance protection start the automatic reclosing device, the third, fourth and fifth stages give definite trip.
The time versus distance characteristic of the five impedance stages is seen in Figure 1. , the characteristics in the impedance plane are in Figure 2.
The single-phase-to-earth and two-phase-to-earth faults is chosen by a zero sequence current relay (3Io) having a biased characteristic.

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.
The distance protection contains a built-in three shot automatic reclosing device with one and three phase reclosing (OR and TR) which is suitable to apply on an effectively earthed network.
If one phase reclosing is set, the protection trips the faulty phase of the CB only on single-phase-to-earth fault, but all the three phase will be tripped on two-phase, two-phase-to-earth and three phase fault. If three phase reclosing is set only, on any fault, the protection trips all the three phase.
The three shot automatic recloser consists one fast reclosing cycle (FR), and two slow reclosing cycles (1SR and 2SR).
Only the first and second stages of distance protection start the automatic reclosing. Similarly, both stages may be set that the protection trips the CB in one phase only on single-phase-to-earth fault. This parameter setting may be made at first fault (if there is FR or 1-2SR), at a fault after the FR (if there is 1-2SR), at a fault after 1 SR (if there is 2SR), and at the definitive trip.
The first trip of the distance protection may be set to be selective or step acceleration. The same may be set at a trip after FR, after 1 SR and at the definite trip. The step acceleration means the second stage operates without time delaying [t(Z2<) = 0].
PROTLOG logical system is built into the distance protection by the PROTECTA Co. Ltd. The essence of the system is the user can create equations of Boole algebra for the input variables. The equations operate the output variables if the equations are realised. 32 input signals and 19 output signals are used in the PROTLOG system built in the protection. The number of the output signals determines the highest number of equations to be created.

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	1,3xUn 4xIn 100xIn (In=1 A), 50xIn (In=5 A)
Dynamic current limit	100xIn
Accuracy, impedance relays, (over 50% In) Accuracy, current relays, ( over 50 % In) Accuracy, timers	± 5% ± 2% ± 3 ms (10 ms steps) ± 12 ms (1 s steps)
Hysteresis, impedance stages	15%
Reset ratio, current relays	95%
Binary inputs opto-coupled	16 pcs, +8 as an option
Output relay contacts	20 pcs
Type of contacts: with fixed connection: R 1TRIP, S 1TRIP, T 1TRIP, R 2TRIP, S 2TRIP, T2TRIP (all NO), healthy-to-work signal (NC) programmed with matrix: 12 pcs, NO in factory, but changed on ordering
Output contacts, electrical data: rated switching voltage continuous load current making current DC breaking capability at 220 V, at pure conductive load at load ofL/R =40 ms	250 V 8 A 16 A 0,25 A 0,14 A
Auxiliary DC voltage voltage tolerance	220 V or 110 V 88 V to 310 V
Permissible ambient temperature	0^o to 50^o 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 test (ESD; IEC 801-2)	8 kV
Burst test, (IEC 801-4)	2 kV
Setting ranges:
Impedance stages on real axis, R1 on imaginary axis, X1	(0-10000)(10CuCi) mOhm step 10(10CuCi) mOhm(0-10000)(10CuCi) mOhm step 10(10CuCi) mOhm
Setting of directional relay, angular coefficient on X axis, -R1/X1 angular coefficient on R axis, -X1/R1	0-50%, step 1% 0-50%, step 1%
Z4, direction	1/0 (1=forward, 0=backward)
Z5, direction	1/0 (1=forward, 0=backward)
Line impedance for fault locator Xn(line)(10Cu*Ci)	100-5000 mOhm, step 10 mOhm
3I₀ zero sequence current mixing, a	0-100%, step 2%
3I₀ fault detector, basic sensitivity	10-50%, step 1%
3I₀ fault detector, biasing	5-30%, step 1%
The factors found in above parameter equations: (10CuCi)=Un / (10In)
CT rated current	50-1500 A, step 25 A
Phase O/C relay, I>/In (operates VT midget CB trip only)	30-2500%, step 5%
Voltage stage, U<>/Un	0-100%, step 2%
Voltage stage type, U<>	0/1 (0=overvoltage, 1=undervoltage)
Impedance stage timer (except first stage), t	0-60000 ms, step 10 ms
Phase OC timer, t(I>)	0-60000 ms, step 10 ms
Voltage stage timer, t(U<>)	0-60000 ms, step 10 ms
Healthy-to-Work failure Signal timer, t(fail)	0-600 s, step 1 s
Timer of equtions, t	0-60000 ms, step 10 ms
FR i HR dead time	0-60000 ms, step 10 ms
SR dead time	0-600 s, step 1 s
External communication	RS 232/optical fibre cable
Optical cable operating mode	radial or loop
External communication speed (BaudRate)	150 to 19200, step 2x
Daily automatic self-check time	0 to 23 h 59 min, step 1 min
Automatic self-check block	setting to 60 min
No. of devices within a system	0-254
No. of devices within a substation	0-254

Design, size

An EuroProt device is always rack mounting. It has two design forms. One of the form 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

Width	Height	Depth
483 mm	132,5 mm	201 mm

Outline size of panel mounted device

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 (see separate information sheet)
longitudinal differential protection
SCADA connection (see EuroProt system information sheet)
relay contacts with 4 A breaking capability
toroidal type CT input PCB
8 pcs binary inputs for the PROTLOG operating equations

Data to be ordered

Protection type [DTVA-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]
Options [if required]