SERD is able to support you for High- and Medium-Voltage–Bushings in general:
Bushings with modern high performance Silicon-Insulators are SERD standard. Ask SERD for support!
40MVA Transformer
SGB -SMIT Transformer GmbH
Every phase conductor & neutral conductor equipped by Silicon-Composite-Bushings of SERD Type SIDI 12
High Current Bushing 52kV; 12,5kA,         
Type SIDI 52-130 (12,5kA)         
  SIDI Standard- Series up to 52kV
with standard & prolonged creepage length
          Leaflets are available on request!
High-Current-Bushings available until 25 kA!
  High Current Bushing 24kV; 4 kA
Type STC 24-4000

  Retrofit of Bushings of all Brands
  • - Incoming inspection: Diagnose, Dielectric test: C, tan-δ and AC voltage test including partial discharge
  •    measurement.
  • - Comparison with original values (as known) or with empirical values.
  • - Recommendation for Repair, Retrofit or Re-New of Bushings.
  • - Offer with cost for further action.
  • - Waste Disposal and/or refurbishment of aged or defect parts (waste disposal in compliance with the laws if e.g. dioxin containing)
  • - Final Quality Test : Power Frequency Test including Partial Discharge measurement,
  • - Repeating of Type Tests in general or partly as requalification

Examples of successful Retrofit Action: From Reports of our Customers
Generator -Bushing 24 kV, 8 kA
Beginning with stocktaking and visual inspection, the dismantling for failure analysis will be documented
and described in detail. Type-Nameplate showed: Capacity 270 pF; Tan-δ 0,55%
  Inspection and visual incoming inspection:
Tan-δ and Capacity-check Lock-fixation ring “A” to loosen for dismantling . Red: Epoxy- Insulator.
  The dismantling of the fixation-rings „A“ revealed strongly adhering, crusted coal-dust contamination, which penetrated from the outside abetween the insulator and the O-ring. The O-ring seals are for the most part destroyed.
  As shown on the left side of the picture, we revealed remarkably more dust contamination in the course of further dismantling of fixation –ring, seal O-ring and epoxy insulator.
  Interior view of dismantled Epoxy –Insulators: heavy contamination on both sides and crystalloid filled in isolation visible. After cleaning refurbishment and inspection, the insulator was qualified as reusable.
  Detail of inner surface at the Bushing -grading area with penetrated contamination.
The grading part of this Bushing had to be replaced by a new one. All parts except the seals have been recycled. Retrofit valued the bushings as new parts.
  Repair & Retrofit Order: 6 Generator -Bushings 30kV
  • Dielectric Test & Partial-Discharge-PD-Measurement
  • Condition analysis and Customer-Report towards Retrofi
  • Offer including schedule / Check and customer-order
  • Dismantling, cleaning, and revision
  • Exchange of defect insulators and seals.
  • Re-assembling
  • Dielectric and Tightness Final Tests & Inspection
  • Package and transport
  Porcelain Insulators at incoming and inspection
Condition at incoming:

Damages and traces by flashover- and arcing
  Porcelain-insulators replaced by Retrofit with new insulators:
Dielectric final tests: Power frequency test voltage 50Hz –1 minute with partial discharge measurement as well as capacity- and Tan-δ- measurement after successful Retrofit.
  A SERD Innovation: Generator Bushings with Silicone Insulator
Classic standardized design according to DIN 48124 with capacitor grading Type SERD SG
  Bushing without additional sheds. The state of the art for dry indoor condition.
Grading surface protected by special varnish.
  New produced or under Retrofit respectively repair. – Instead of Porcelain Insulators, 
SERD is able to equip one or both sides of Bushings with Silicone –Insulators.
  SERD Generator Bushings with
Silicon- Insulation on outdoor air side

Typ SG 24,5- L 120

24,5kV , 10 kA