Low oil level alarm on protecting transformers Thermal overload relay protection measures thermal time constant of transformer’s windings and provides protection accordingly.Ĭhecklist for substation operators when transformers trip off on faultĬheck all relevant relay panels and follow protection flagsĬontact control room and report the fault The most common relays used for transformer protection include differential relay, over flux relay, Buchholz relay, OLTC Buchholz relay, PRV relay, OT Trip relay, WT Trip relay and overload alarm relay. Transformer relays provide control, basic protection and backup protection including current differential and restricted ground differential and over current protection. Six common protections for transformers are against overheating, over current, earth fault, gas detection relay or Buchholz, over fluxing and differential protection of transformer. The faults that occur in the transformer include earth faults, core faults, interturn faults, phase-to-phase faults, tank faults and other external reasons. The control room staff must be duly informed about the situation, along with the reason for the fault. In such a situation, the substation operator must inspect relay panels and transformer visually. With such information, they could react effectively and immediately to transformer faults.įor instance, when substation transformers are tripped off on fault due to poor wiring conditions, they would not energize it because combustible gases are present in transformer tank and the voltage levels must be limited. Reacting to faults is simpler when the substation crew is kept informed about the transformer’s internal function and the logic behind it. Specifications Input Ranges: 24 field selectable ranges via switch settings Voltage: 0-50 mV to 0-10 Vdc Bipolar Voltage: ±5 Vdc or ☑0 Vdc Current: 0-1 mADC to 0-20 mADC, 4-20 mADC Input Impedance and Burden: Voltage: 250 kΩ minimum Current: 50 Ω typical Voltage Burden: 1 Vdc at 20 mA current input Isolation: 1200V Isolation: power to input 600 Vac or 600 Vdc common mode protection Input Loop Power Supply: 15 Vdc ☑0%, 25 mADC maximum ripple, less then 10 mV rms may be wired for sinking or sourcing mA input Relay Output: Single setpoint dual DPST contacts, field configurable 2 Form A (NO) and Form B (NC) contact sets (8 terminals) may be wired for C Form operation Relay Contact Ratings: 8 Amps 240 Vac resistive load 5 Amps 240 Vac inductive load 8 Amps 30 Vdc resistive load 3.5 Amps 30 Vdc inductive external contact protection such as a RC snubber is recommended for inductive loads Set Point: 12 turn potentiometer adjustable from 0 to 100% of span Deadband: 12 turn potentiometer adjustable from 1 to 100% of span Response Time: 70 milliseconds typical Functional Test/Reset Button: Toggles relay to opposite state when pressed resets latching relay if latching relay mode is selected Ambient Temperature Range and Stability:-10 to 60☌ (14 to 140☏) operating ambient better than 1% of span over operating temperature range better than 0.02% of span per ☌ Power: 60 to 265 Vac, 50/60 Hz or 85 to 300 Vdc, 2W maximum DC Versions: 9 to 30 Vdc or 10 to 32 Vac, 50/60 Hz, 2W maximum Housing: Mounts to standard 35 mm DIN rail, IP40 rating Connectors: Four 4-terminal removable connectors 14 AWG maximum wire size Dimensions: 22.5 W x 117 H x 122 mm D (0.89 x 4.62 x 4.Though transformers are equipped with precautionary methods to ensure plant’s performance and longevity, it is important to be updated constantly with what is happening within the apparatus. The alarm output can be field configured for HI or LO operation, latching or non-latching, and normal or reverse acting. The unit provides a single setpoint adjustment of the two DPST relay contacts. Front accessible potentiometers are used to adjust the alarm setpoint from 0 to 100% and the deadband from 1 to 100%. Heavy-duty relay contacts allow the module to directly control high capacity loads. Offset ranges such as 1 to 5 Vdc and 4 to 20 mAdc are also included. 15 voltage and 9 current input ranges can be field configured via external rotary and slide switches. The DMD1080 accepts a DC voltage or current input and provides visual alarm indication and alarm relay contact outputs.
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