Type CTMM/CTMFM Motor protection relay Type CTMM/CTMFM Motor protection relay CTMM relay withdrawn from case Features Application I2 conscious thermal protection. Selectable thermal characteristics. Built-in stalling protection with There is a wide range of Motor and Motor characteristics in existence, because of the numerous duties for which they are used and all of them need protection. Fortunately, the more fundamental problems affecting the choice of protection are independent of the type of motor and the type of load to which it is connected. provision for external control. Sensitive earthfault protection suitable for either residual or CBCT feed, with instantaneous or time delayed operation option. Pre-trip alarm with adjustable pickup and time delay with LED indication. Separate unbalance detection with wide setting range and instantaneous or time delayed operation option. Thermal memory for several minutes, during auxiliary supply failure. Local/remote resetting facility for thermal element. Auxiliary supply supervision with alarm and LED indication. Suitable for ac or dc aux. supplies. Motor characteristic must be carefully considered when applying protection. While this may be regarded as stating the obvious, it is emphasized because it applies more to motors than to other items of power system plant, e.g. the starting and stalling currents and times must of necessity be known when applying overload protection and furthermore the thermal withstand of the machine under balanced and unbalanced loading must be clearly defined. 2 The protection usually provided for three phase motors, while generally effective against overloads and short circuit conditions, rarely take into full account the harmful effects of unbalanced line currents. Even a modest unbalance can cause damage to a motor by overheating and in the extreme instance of motor stalling due to loss of one phase, severe rotor damage can occur within the normal starting time. The static motor protection relays type CTMM and CTMFM measure the load current and the unbalance current independently, and provide accurate protection against thermal damage under all operating conditions. The thermal characteristic of the relay is designed to follow closely the thermal withstand characteristic of typical motors; this ensures that the relay isolates the motors only when the insulation life is threatened. The features in the CTMM/CTMFM relays include the following: a) A built-in stalling protection, I1(t), has been included and it is a standard fitment for both the versions. When specified, it can be either permanently in or effective only under external control. b) I0 unit is offered with an adjustable time delay setting and is suitable for either residual CT connection or CBCT connection. c) A pre-trip alarm unit has been added as a standard fitment for both versions along with a self extinguishing LED indication. d) Remote thermal reset facility is available for both versions. e) Thermal memory against aux. supply failure lasting for several minutes is provided for all relays. f) The same relay can be used for both ac or dc auxiliary supplies. Also external resistors permit the same basic relay to be accommodated with different auxiliary voltages. g) Aux. supply monitoring is provided on all versions with healthy indication and unhealthy alarm contact. h) Most of the current and time setting adjustments are with binary switches. This provides a wider setting range with better resolution and accuracy (see Figure 1). The range of types CTMM and CTMFM relays, manufactured to suit various applications of motors, controlled by either circuit-breakers or fused-contactors is shown in the Table I. Figure 1: Typical name plate details These three operating characteristics in the different executions of the relay are selected from 11 cold curves with 11 hot curves having hot-to-cold ratio of 0.33 (standard) and 11 more hot curves having hot-to-cold ratio of 0.66. This extensive choice of characteristics thus gives great application flexibility for the relay. One group in the series, designated CTMFM, has been designed for motor control centre applications where fused-contactors are used. These relays include a time delayed single phasing element and an earthfault element which, in the event of the fault level being above the rupturing capacity of the contactor, allow the fuse to blow before the contactor operates. Circuit description To cater for a wide range of motor characteristics, three alternative operating characteristics are provided on thermal units, selectable by a switch on the relay front panel. Figure 1 shows the block diagram of CTMM/CTMFM relays. The inputs connected in each phase of motor supply are fed to a sequence filter network which separates the positive 3 and negative sequence components (I1 and I2) of the input current. These quantities are in turn fed to separate thermal setting potentiometers. Instantaneous operating element I1 is placed between the sequence filter network and thermal setting potentiometer. The potentiometers provide two output voltages which are proportional to the positive and negative phase sequence components of the input current. The voltages are fed into squaring circuits to give voltages proportional to (I12) and (I22). Table I (only standard curves and references are included) Application considerations Typical co-relation of relay and motor types Protection provided Motor Submersible controlled by pump motors Thermal Circuit breaker CTMM 101/104 CTMM 101/104 CTMM 102/105 CTMM 103 Thermal, instantaneous three phase overcurrent, Circuit breaker CTMM 301/304 CTMM 301/304 un-balance and single phasing CTMM 302/305 CTMM 303 Thermal, instantaneous three phase overcurrent, unbalance and single phasing earthfault and separate built-in stalling protection. CMR motor Standard industrial motors Circuit breaker CTMM 501/504 CTMM 501/504 Special motors for high inertia loads CTMM 502/505 CTMM 503 Thermal, unbalance and single phasing and earthfault Fused contactor CTMFM 301/304 CTMFM 301/304 CTMFM 302/305 CTMFM 303 Thermal, unbalance and single phasing, earthfault and separate built-in stalling protection. Fused contactor CTMFM 401/404 CTMFM 401/404 CTMFM 402/405 CTMFM 403 Note: This is only typical recommendation. Actual model to be choosen after considering the thermal characteristics of motor. Refer to the commercial department for further assistance. Overload protection/thermal element (Th) The output voltages from the squaring circuits are added in order to get the voltage proportional to I12 + 6I22. The feed-back circuit of the integrator causes the output voltage of the integrator to rise exponentially upto 105% of the relay setting current and linearly above that setting. The output of the integrator is fed into a level detector which, when the set voltage is reached, energises an electromagnetic output unit. This operates two pairs of electrically separate contacts which are used to trip the circuit breaker or fused contactor controlling the supply to the motor. Thermal memory has been provided against auxiliary supply failures. This is achieved by opening out the discharging path of the timing capacitor by a N/O contact of a separate relay that operates from the regulated power supply. Thermal element can be reset using a push button provided on the front panel which initialises the integrator. Figure 2: Typical block diagram (CTMM 501 - 510) 4 The same feature can be established by remote control also. Using a curve selecting switch provided on the front panel three different thermal operating characteristics are obtained. Thermal alarm element (Th (A)) Voltage proportional to I12 + 6I22 is fed through an averaging circuit to a level detector, which, when the set voltage is reached, initiates a linear integrator for timing. This energises a separate thermal alarm relay after a fixed time delay (25 sec., 50 sec., or 75 sec. selectable in the PCB). This element has one N/O contact wired out externally and is provided with a self reset LED indication. A thermal pre-trip setting can be set on the relay at any value between 70-90% of thermal-trip setting by a rotary switch provided on the front panel. Over-current and short-circuit protection element (instantaneous I1) The instantaneous I1 element for overcurrent is connected in the appropriate output of the sequence filter and is continuously adjustable over the setting range (600%1200% of relay rated current). During overcurrent condition, this energises an electromagnetic output unit with two pairs of electrically separate contacts, after 100 ms delay. This 100 ms delay in operation is provided to prevent false tripping by transient starting currents. Stalling and prolonged starting protection element (I1 [t] ) The positive sequence component of the input current from the sequence filter is fed to level detector which compares the voltage proportional to the peak value of the input with the set voltage and initiates a counter for timing, when the set voltage is reached. This energises an electro-magnetic output unit with two electrically separate contacts, after the set time delay. Both current setting and time setting are provided by binary switches. I1(t) element can either be permanently included in the circuit or included only on external command depending on the I1(t) control switch position on the relay front panel. Single phasing and unbalance protection element (I2) a simple shunt regulator. Auxiliary supply monitoring is provided with healthy indication by a LED on relay front panel and unhealthy alarm contact of the dc monitoring relay. The negative sequence component of the input current from the sequence filter is fed to a level detector which compares the voltage proportional to the peak value of the input with the set voltage and initiates a counter for timing, when the set voltage is reached. This energises an electromagnetic output unit with two pairs of electrically separate contacts after the set time delay. For type CTMFM motor protection relays, instantaneous I1 element for overcurrent is eliminated from the circuit. Otherwise, the remaining details are as mentioned for type CTMM relay above. Both current setting and time setting are provided by binary switches. Current ratings (In) Earthfault protection element (I0) Frequency rating During earthfault condition, the zero sequence component of the input current is fed to a level detector which compares the voltages proportional to the peak value of the input with the set voltage. It initiates a counter for timing, when the set voltage is reached. This energises an electromagnetic unit with two pairs of electrically separate contacts, after the set time delay. The variants available for type CTMM/CTMFM relays are shown in Table II. Technical data 1A or 5A. 50 Hz. Current settings Settings are expressed as percentage of the relay rated current. Thermal current (Ith) 70% - 130% continuously adjustable. (Lower range available. Details on request.) Dual current setting ranges and time setting are provided by binary switches. Instantaneous overcurrent element (I1) Current setting range can be selected by a selectable range switch on relay front panel. This wide range of current setting ensures that I0 element is suitable for either residual CT connection or CBCT connection. Instantaneous or time delayed unbalance element An adjustable external stabilising resistor can be connected to the I0 element, to ensure stability especially when, under motor starting conditions unequal saturation of current transformers might otherwise cause operation of the relay. Alternatively, I0 element can be used without the stabilising resistor, but with a small time delay setting through an option available on the relay. An auxiliary supply, either ac or dc, is used to energise the electronic circuits in the relay. This is stabilised within the relay by 5 600% - 1200% continuously adjustable (other settings on request) - for CTMM only. 30% - 630% in 15 steps of 40% adjustable by a 4-position binary switch. Earthfault element (I0) Dual range 10 - 160 mA/50 - 800 mA in 15 steps of 10/50 mA adjustable by a 4-position binary switch (for residual CT or CBCT applications). External resistor i) 500 W for 1A relay. ii) 27 W for 5A relay. Stalling protection (time delayed overcurrent unit I1 (t) ) 150% - 600% in 15 steps of 30% adjustable by 4-position binary switch. (Alternative ranges available. Details on request.) Pre-trip alarm unit 70% - 90% of thermal trip setting in 9 steps of 2.5% adjustable by rotary switch. Operating time a) Type CTMM relays Ith element: A total of 11 operating characteristic curves (see Figure 3) are available, in combinations of 3, each of the three curves being selectable by a switch on the front panel. I1 element: 100 ms nominal at 2 times setting. I2 and I0 element: 60 - 125 ms (fixed). Alternatively, adjustable between nominal values of 0.5 to 7.5 secs. in 15 steps of 0.5 second. The latter for use when setting chosen is low, or when used without a stabilising resistor. Time delay separately adjustable for I2 and I0 units. I1 (t) element: i) 4 - 60 secs. in 15 steps of 4 secs. adjustable by 4-position binary switch (standard). ii) 2 - 30 secs. in 15 steps of 2 secs. adjustable by 4-position binary switch (on request). Table II Variants of CTMM/CTMFM relays Relay Description of units type Thermal Instantaneous ref. CTMM 101110 X CTMM 301310 X X X CTMM 501510 X X X X CTMFM 301310 X X X CTMFM 401410 X X X case size 1½D X 2D 1½D X 2D Note: 1. Thermal element is always provided with the following: 1.1 Thermal trip (Th) and pretrip alarm unit [Th (A)] 1.2 Thermal memory 1.3 Local and remote thermal reset New ref system C T M F M 4 0 3 C T M M 3 0 2 New curve ref. No. of elements Accuracy Temperature limits: Current setting: All units operate satisfactorily over the ambient range 20°C to +55°C. The variation in parameters is less than the above accuracy tolerances over the range 5°C to +40°C. i) Thermal element (Th) ±3% of nominal pick-up. ii) Elements I1, I2, I0 & I1 (t) ±10% of nominal setting. Time setting: i) Time delayed elements I1(t), I2 & I0 Fixed time delay 25s, 50s or 75s selectable by link on PCB. ±10% of nominal setting or ±25 ms whichever is higher. b) Type CTMFM relays Thermal element (Th): All operating time data as per CTMM relays except that I1 element and its timings are not applicable. ±10% of nominal operation time at 5 x the equivalent current setting for hot and cold curves. The thermal element begins to operate at 1.05 times nominal setting current. I1 (t) 1½D Pre-trip alarm unit (Th (A) ): Pick-up current I0 I2 I1 Relay Frequency variation: In operation all parameters vary less than above accuracy tolerances over the normal frequency (50 Hz): 4751 Hz. 6 Thermal overshoot Less than 2%. Thermal reset facility i) Local reset By push button on relay front panel. ii) Remote reset By external command through potential-free N/O contact. Thermal memory (against auxiliary supply failure) For several minutes. Stalling protection I1 (t) Built-in, when specified on all relays. Facility provided to keep this permanently in operation (permanent mode) or on external command (controlled mode) through speed switch or a timer, for covering special applications. Modes selectable by switch on front panel of relay. Insulation 2 KV, 50 Hz, for 1 minute between all circuits and the case and also between all separate circuits. 1 KV, 50 Hz, for 1 minute between normally open contacts (to IS 3231 and IEC 255-5). Contacts Trip units: 2 pairs of contacts (N/O and/or N/C) self reset. Make and carry 7500VA for 0.5 sec. with maxima of 30A/660V. Auxiliary supplies Pre-trip alarm unit: The ratings: One pair of N/O self reset contact. Make and carry and break 35W with maxima of 500V 2A ac/dc resistive. The basic relay is designed for operation from either ac or dc of 30V rating. The relay is, however, suitable for other ac/dc voltage supplies by using recommended values of external resistances. Details supplied on request. However, standard values of rated voltages available are: 30V, 50V, 110V, 220V and 250V (either ac or dc). Other ratings also are available on request. Operative ranges: 80% - 110% of rated voltage. Monitoring: Auxiliary supply monitoring One pair of N/O or N/C contacts as required. Make and carry and break 50W subject to maxima of 250V dc/ ac, 5A dc/ac with resistive circuit. Operation indicators (i) Hand reset indicator (mechanical) on I1 (for CTMM only), I2, I0, Ith and I1 (t) units. (ii) Self resetting LED for pre-trip alarm units. Aux. supply continuously monitored by LED on front panel. Aux. supply failure annunciation by single N/C contact suitably wired out (N/O contact on request). Overload ratings Impulse voltage withstand Note: 5 KV peak and 1/50 microsecond wave form applied both transversely and between relay terminals and earth in accordance with IS 8686 and IEC 255-5. I0 element withstand: Max. setting High frequency interference test Relay meets the IS 8686 and IEC 255-22-1 Appendix-D to Class-III. (i) Continuous withstand - Relay setting current. (ii) For 0.5 second - 100 times relay rated current. continuously and 100 x setting for 3 seconds. Burden AC burden (i) Less than 1VA/phase at rated current. (ii) I0 element 0.006m VA at setting current at 10 mA setting. DC burden Basic relay less than 6 watts. 7 Figure 3: Application diagram Figure 4: Thermal characteristic curves 8 Information required with order Table III (for user to fill in) Customer Motor details Synchronous induction control c.b. by contr. rated volts currt. if under rated % connd. load type of load thermal curve ref. stator time const. stalling currt. stall withstand starting ref order enquiry CT details ratio /1A /5A VA class accy. Imt facr. type cbct convnl. Relay specn. aux. supply hot cold d.o.l. asstd. details currt. time hot restarts, if reqd. fuse and contactor details if applicable mts amps secs secs amps secs no. 9 if ac, derived from: contacts (max. 2 per unit) units reqd. (for combns see Table I) I0 unit for if cbct. v.dc v.ac n.o. I1 I2 n.c. I0 Ith I1 (t) cbct residual conn. p.o.c. reqd. A overall cable dia cm ALSTOM Limited Pallavaram Works: 19/1, GST Road, Pallavaram, Chennai-600 043. India. Tel: 91-044-2368621 Fax: 91-044-2367276 Email: plw.applications@alstom.sprintrpg.eml.vsnl.net.in. © 1998 ALSTOM Limited 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 advice on the application of any product referred to in it. ALSTOM Limited cannot be held responsible for any reliance on any decision taken on its contents without specific advice. PR:018:0199:A Printed in India.
