1. DISTRIBUTION TRANSFORMERS (UPTO 2500 KVA, 33 KV CLASS)
A. Hermetically sealed oil transformers
B. AMORPHOUS CORE TRANSFORMERS
Amorphous core transformers significantly reduce no-load losses by using an amorphous alloy for the iron core, which the transformer windings that carry the electricity are coiled. The expected reduction in energy loss over conventional (Si Fe core) transformers is roughly around 70%, which is quite significant. By using an amorphous core – with unique physical and magnetic properties – these new type of transformers have increased efficiencies even at low loads – 98.5% efficiency at 35% load.
C. CAST RESIN DRY TYPE TRANSFORMERS
D. ENERGY EFFICIENT TRANSFORMERS
2. POWER TRANSFORMERS (UPTO 50 MVA, 132 KV CLASS)
Special Features:
• In adherence to IS and IEC standards
• Mineral Oil, Ester Oil as per customer requirement
• Copper / Aluminum windings as specified
• High permeability core laminations with step-lap construction
• Conventional type and hermitically sealed tank construction
• Seal breathing system (SBS) Keeps transformer isolated from atmospheric moisture, thus enhance the transformer life Due to Sealed Breathing System & activated alumina, the main transformer will not require oil filtration for at least 15 years.
• Thermosyphen filter is an ON LINE Transformer Oil Preservation system for Power Transformers.. The system basically consists of a container containing Absorbent (Normally Activated alumina) which has very high moisture absorption capacity.
• Electrostatic shield earthing is a shield provided between LV & HV coil. Thus avoiding transfer of surge/impulse voltages passing through inter-winding capacitance.
A. SINGLE PHASE TRANSFORMERS
B. SPECIAL APPLICATION TRANSFORMERS
• Converter/inverter duty
• Furnace duty
• Neutral grounding transformers
• Auto transformers
• Generator transformers
• Solar transformers
CONDITION MONITORING AND SITE MAINTENANCE OF TRANSFORMERS
There are three types of maintenance jobs on transformers
a. Routine or periodic maintenance
For example, maintenance of OLTCs, after set number of operations or time frame
b. Condition based maintenance
For example, improvement of the insulation values.
c. Breakdown maintenance / repair
For example, failure of a bushing .
Each one has different criteria to execute the work.
The biggest enemy of transformers is moisture. If we fail to protect the transformer from moisture, the life of transformer may reduce to half or 1/4th in inverse proportion to moisture levels.
Generally, Life of transformer = Life of transformer insulation
Insulation degradation happens either due to moisture entry or excessive temperature of insulation OR both simultaneously.
Generally, the permitted moisture level in transformer is < 1% by DWOI.
Transformers operating in the field above 2.5% moisture levels come under danger zone and 3.5% moisture level indicates that transformer is lying on death-bed.
Many transformers do not complete their rated defined life of 25 years due to various reasons. While many factors like design, workman-ship, operating conditions etc. play an important role, but degree of dryness and loading of a transformer defines its life.
On the other hand, many transformers give satisfactory services for 40-50 years. This can be extended to 50-60 years by intelligent use.
Routine and periodic maintenance is generally defined by the manufacturer and relevant standards.
Breakdown maintenance does not give us time to act as per our wish and force us to adopt the shortest way to restore the power.
It is condition based maintenance where we have to be very careful in pre-qualifying the transformer for a certain work. For example, it will be a stupidity to carry-out dry-out, vacuum application and heating of a transformer in which DP value of paper is 300. Such a transformer, with a brittle insulation, can get damaged even if it is shifted from one place to another. An immediate wise action would be to reduce load on the transformer to extend its remaining life, rather than going ahead for overhaul work.
RLA study can be done on a transformer to know its app. remaining life.
The following tests must be conducted on a transformer for RLA:
The following tests must be conducted on a transformer for RLA:
A. IR values/ PI values
B. C & Tan delta values of windings and bushings
C. Measurement of degree of dryness of a transformer by RVM or alternate method
D. Magnetizing current drawn by transformer
E. Impedance check
F. DC winding resistance measurement on all taps/ all windings
G. Sound and vibration levels
H. SFRA
I. Tests on oil
i. Water content
ii. Specific resistance
iii. Tan delta
iv. Acidity
v. IFT
vi. DGA
vii. Furan analysis
J. Status of OLTC
K. Status of oil leakages
