Type MCAG 14, 34 T&D. High Stability Circulating Current Relay

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1 PROTETION Type MAG, 3 High Stability irculating urrent Relay The MAG relay, used with a stabilising resistor, is designed for applications where sensitive settings with stability on heavy through faults are required, and is recommended for balanced and restricted earth fault, bus-zone and certain forms of differential protection for generators, auto-transformers, reactors and motors. The relay operates as a high impedance unit protection scheme. The relay is an attracted armature unit of simple and robust construction. The operating coil of this unit is connected in series with a small choke and capacitor, forming a series resonant circuit. These components are energised from an auto-transformer which is tapped to provide seven current settings. Due to the simple electromechanical construction, the detection element, and the output contacts are one and the same device. Operation is therefore fast, and highly reliable. The relay circuit, tuned to the supply frequency, rejects the harmonics produced by current transformer saturation. The total impedance of the relay and series stabilising resistor is usually low enough to prevent the current transformers developing voltages over kv during maximum internal faults, but in some applications a non-linear resistor is required to limit this voltage. Types MAG and MAG 3 relays are single and triple pole, respectively. ustomer enefits High stability with through faults Tuned to rated frequency Operates in 5ms at 5 times setting T&D

2 APPLIATION When circulating current protection schemes are subjected to heavy through faults, the sudden, and often asymmetrical growth in the system current can cause the protective current transformers to approach or even reach saturation level. This may result in a high unbalancing current due to the variations in the magnetising characteristics of the current transformers. To ensure stability under these conditions, it is common practice to use a high impedance relay, set to operate at a voltage slightly higher than that developed by the current transformers under maximum external fault conditions. A URRENT TRANSFORMER REQUIREMENTS MAG relays are suitable for use with.5a, A and 5A current transformers, at 5Hz or 6Hz. Since selection of the optimum relay setting is based on the loop resistance of the secondary circuit, there are advantages in using current transformers with either of the lower secondary ratings. The current transformers used in high impedance circulating current differential protection systems must be equal turns ratio and have reasonably low secondary winding resistance. urrent transformers of similar magnetising characteristic with low reactance construction such as IE6 lass PX, or similar, are preferred. The relay requirements are based upon a calculation of the required knee-point voltage with the IE definition of the knee-point voltage being the point on the magnetisation curve at which a % increase in excitation voltage produces a 5% increase in excitation current. The required stability voltage setting (Vs') and minimum knee-point voltage (Vk) are calculated as follows: Note: All three elements are identical. Only one is shown Alarm Trip 3 A Figure IA I I Stabilising Resistors T shorting ontacts Internal and external circuit diagram for unbiased differential protection of generators, reactors and synchronous motors using type MAG 3 relay Where Vs' If (Rs+Rp) VsA = VA + Ir Rsr Ir Vk VsA If = maximum secondary through fault current Ir = relay setting current Rct = T secondary winding resistance RP = maximum loop lead resistance between Ts and relay Rsr = external stabilising resistance VA = relay burden at setting VsA = Actual voltage setting Figure Type MAG relays applied to restricted earth fault protection of power transformer External stabilizing resistor 8 External metrosil (if required) N.E.R. External stabilizing resistor External metrosil (if required) 8 MAG >3 MAG Simple, reliable and secure unit protection

3 STAILISING RESISTANE Externally mounted, continuously variable resistors of Ω, Ω and Ω for.5a, A and 5A T secondaries respectively are supplied as standard. The appropriate value of series resistance (Rsr) required to ensure stability is calculated as follows: Where Rsr = Vs' - VA / Ir Ir Vs' = minimum required stability voltage VA = relay burden Ir = relay setting current a) Mounting clip for stabilising resistor EFFETIVE PRIMARY OPERATING URRENT During internal fault conditions, the relay and Metrosil current and the magnetising current of all connected current transformers are supplied from fault current. The primary operating current is given by: Where I op = n (I R + NI m ) I R = relay setting current (plus Metrosil current at setting voltage if used) I µ = current transformer magnetising current at setting voltage (A) N = number of connected current transformers n = current transformer turns ratio SIDE VIEW.5 TOP VIEW 8. SLOT.5 5 γ b) Stabilising resistor M6 learance METROSIL (NON-LINEAR RESISTORS) A Metrosil is required to limit the T output voltage under an internal fault condition if the peak voltage developed (Vp) is greater than 3kV. The voltage spike (Vp) due to T saturation is calculated from: Vp = VkA (Vf-VkA) Vf = If int (Rs+Rp+Rsr+ VA ) Ir Figure 3 External stabilising resistor assembly To ensure that the thermal rating of the stabilising resistor is not exceeded, it is recommended that the resistor is not set to a value less than 65% of its maximum rated value. For example, a Ω variable resistor should not be used when the required stabilising resistance is less than Ω. In certain applications there is no need to utilise stabilising resistors in series with the MAG/3 (indicated by negative stabilising resistor value) because the impedance of the relay elements alone will offer sufficient stabilisation. Where Ifint = maximum secondary internal fault current VkA = actual T knee-point voltage The exact Metrosil rating will depend upon the application and is based upon the following details: T secondary current rating Relay stability voltage (VsA) Maximum secondary internal fault current in Amps (Ifint) The outline and mounting arrangement drawing for the external Metrosil units is shown in Figure. The outline and mounting arrangement drawing for the external stabilising resistor is shown in Figure 3. Figure Outlines external Metrosil units Insulating Spacer M6 ISO Terminals 5 M ISO Stud 8 mm - mm Fixing Holes All dimensions in mm 5. 9 ±

4 TEHNIAL DATA > Rated frequency 5Hz and 6Hz > urdens VA at setting > Standard current settings 5% - %, % - % or % - 8% of.5a, A or 5A (T secondary), adjustable by plug setting bridge in seven equal steps. > Operating time 5ms at 5 times setting current. See figure 5. > Thermal withstand Relay 5 times tap setting continuous times tap setting for 3s Stabilising Resistor Resistor Maximum urrent Withstand (A) Value (O) () ontinuous 3 second () second () () - The resistance tolerance is ±% () - The 3 second & second rating values are AREVA calculated values Operating Time in Milliseconds Multiples of Pick Up > ontacts Two pairs of make self-resetting contacts are provided on single element relays and two on three element relays. In three element relays the contacts are connected in parallel, as shown in Figure, or brought out to separate case terminals if required. ontact Rating Figure 5 Time/current characteristic Make and carry continuously ac 5VA with maxima of 5A or 3V dc 5W with maxima of 5A or 3V Make and carry for 3s ac 5VA with maxima of 3A or 3V dc 5W with maxima of 3A or 3V reak ac 5VA with maxima of 5A or 3V dc W (resistive)5w (inductive) with maxima of 5A or 3V >5 Simple, reliable and secure unit protection

5 > High voltage withstand Dielectric withstand IE 655-5:9 kv rms for minute between all terminals and case earthkv rms for minute between terminals of independent circuits, with terminals on each independent circuit connected togetherkv rms for minute across open contacts of output relays. High voltage impulse IE 655-5:9 Three positive and three negative impulses of 5kV peak,./5µs,.5j between all terminals of the same circuit (except output contacts) between independent circuits, and between all terminals connected together and case earth. > Electrical environment High frequency disturbance IE lass III.5kV peak between independent circuits and case..kv peak across terminals of the same circuitno additional tolerances are required for the operating time of the unit's thresholds. EM ompliance 89/336/EE ompliance to the European ommission Directive on EM is claimed via the Technical onstruction File route.generic Standards were used to establish conformity. EN 58-:99 EN58-:995 > Product safety 3/3/EE ompliance with the European ommission Low voltage directive EN6-:993/A:995 EN695:99/A:99 ompliance is demonstrated by reference to generic safety standards > Atmospheric environment Temperature IE Storage and transit -5º to +º Operating -5º to +55º IE old IE Dry heat Humidity IE days at 93% RH and +º Enclosure protection IE 659 IP5 (dust protected) > Mechanical environment Vibration IE g between Hz and 5Hz Mechanical durability Loaded contact, operations minimum Unloaded contact, operations minimum > ases Type MAG (single element) and MAG 3 (three element) relays are supplied in 5TE (size 3) and 3TE (size 6) cases respectively. These are shown in Figures 6 and.

6 holes ø Push button projection max 3 Panel cut-out: Flush mounting fixing details 3 5 min. 5 max. Reset All dimensions in mm Flush mounting Figure 6 ase outline 5TE (size 3) Figure ase outline 3TE (size 6) 9 holes ø Push button projection max 5 Panel cut-out: Flush mounting fixing details 3 5 min. 5 max. Reset 5 5 Flush mounting 6> All dimensions in mm

7 INFORMATION REQUIRED WITH ORDER Information Required with Order Relay Type MAG Number of Elements One Three 3 ase Size 5TE (Size 3) ase for MAG only 3TE (Size 6) ase for MAG3 only S V ontact Wiring Segregated contacts ommon contacts (MAG3 only) S Frequency & Flagging 5Hz 6Hz Without Flag = With Hand Reset Flag = Without Flag = With Hand Reset Flag = T Secondary & Setting Range A D 5 - % Setting - % Setting - 8% Setting 5 - % Setting 5 - % Setting - % Setting - 8% Setting 5 - % Setting - 8% (A & ) / - % () 5 - % (A & ) / - 8% () 5 - % Setting - % Setting - 8% Setting Stabilising Resistor.5A A 5A A D E F J K D F G No Resistor Supplied Standard Resistor for.5a T Rating Standard Resistor for A T Rating Standard Resistor for 5A T Rating Non-standard Resistor ( ohms) Non-standard Resistor ( ohms) Non-standard Resistor ( ohms) Non-standard Resistor (5 ohms) Non-standard Resistor ( ohms) Non-standard Resistor ( ohms) Non-standard Resistor ( ohms) Non-standard Resistor (8 ohms) Non-standard Resistor ( ohms) Non-standard Resistor (5 ohms) Non-standard Resistor ( ohms) Non-standard Resistor (56 ohms) Hardware Issue Suffix Factory Defined

8 AREVA TRAK REORD - HIGH IMPEDANE DIFFERENTIAL PROTETION >> Over 3, MAG schemes delivered since 98 >> Over,5 MFA schemes delivered since 983 >> Simple, reliable, secure AUTOMATION-L3-MAG/3-R-.-9-G - - AREVA -. AREVA, the AREVA logo and any alternative version thereof are trademarks and service marks of AREVA. MiOM is a registered trademark of AREVA. All trade names or trademarks mentioned herein whether registered or not, are the property of their owners RS PARIS - Printed in France - SONOVISION-ITEP AREVA T&D Worldwide ontact entre: Tel.: + () Our policy is one of continuous development. Accordingly the design of our products may change at any time. Whilst every effort is made to produce up to date literature, this brochure should only be regarded as a guide and is intended for information purposes only. Its contents do not constitute an offer for sale or advise on the application of any product referred to in it. We cannot be held responsible for any reliance on any decisions taken on its contents without specific advice.