ISP

ISP

Isolator / Surge Protector

The ISP is the original solid-state AC conducting/DC blocking device designed for the corrosion prevention industry. The ISP product line features the most flexible and wide range of product ratings and applications available to the market. Additionally, the ISP provides the highest levels of AC fault-handling capability - up to the highest typical transmission system faults. With its design features and ratings, the ISP is the preferred device for power utility underground cable decoupling/bonding requirements.

Features and Characteristics

  • Solid-state Design Replaces Polarization Cell Technology
  • No Maintenance Needed
  • Fail-safe Design
  • Self-protection Features Built-in
  • Simple Field Testing Procedures with Standard Equipment
  • Comprehensive Testing Available with the optional In-Situ Tester (IST)
  • Flashing LED Indicates Device Operation
  • No Energy/Power Requirements
  • Unlimited Number of Operations
  • Submersible Enclosure
 
      
  • threshold voltage
  • 12.5 or 20V
  • Other voltages optional
  • AC Steady-State Current (amperes - rms) 60Hz
  • 30, 60, or 90A
  • AC Steady-State Current (amperes - rms) 50Hz
  • 25, 50, or 75A
  • Lightning Surge Current
  • 75kA crest (8 x 20 µs waveform)
  • 100kA (optional)
  • environmental rating
  • NEMA 4X or 6P
  • hazardous (classified) areas
  • Not listed, but uses same general construction as our listed Division 2 (or Zone 2) products
AC Fault Current (amperes-rms) 60 Hz
Catalog Code
1 cycle 3 cycles 10 cycles 30 cycles
7
7,000
5,300
4,200
3,700
24
24,000
18,000
14,000
11,000
35
35,000
28,000
21,000
14,000
68
68,000
55,000
40,000
30,000
118
118,000
96,000
75,000
54,000
AC Fault Current (amperes-rms) 50 Hz
Catalog Code
1 cycle 3 cycles 10 cycles 30 cycles
7
6,700
5,000
4,000
3,600
24
23,000
17,000
13,000
10,000
35
33,000
27,000
20,000
13,000
68
65,000
52,000
38,000
28,000
View Model Number Description Chart
ISP Model Numbers

Literature:
ISP - Technical Literature
ISP - Installation Instructions
ISP - 118kA Version - Addendum to Technical Literature
Installation Instructions for 118kA Version

Support Documents:
Competitive Comparisons
In-Depth Literature

Application Assistance:
Decoupling Power Cable Sheaths/Casings
Insulated Joint Protection
AC Voltage Mitigation

 

Polarization Cells

Comparison of Dairyland ISP to polarization cells

  • The ISP is a solid-state device, flexible in design and ratings, which requires no maintenance over the life of the product.
  • With an ability to block voltage up to 12.5V (optionally 20V), a single ISP can always handle the voltage blocking level needed, as compared to a polarization cell, which blocks up to about 1.2V. This can result in the need to place several polarization cells in series to achieve the required blocking level.
  • Leakage current through an ISP is very low - it presents a high impedance to the flow of DC current, limiting this current to values much lower than polarization cells.
  • While blocking DC current, the ISP appears as a low impedance AC path. Any induced AC current can be safely shunted to ground, resulting in a low induced voltage on the structure.
  • The ISP has various AC fault current ratings, appropriate for the available AC fault current from the electrical system. Device switching is instantaneous, presenting a virtual dead-short between the connected points.
  • The ISP is generously rated for lightning surge current conditions. Polarization cells do not have a published rating for lightning.
  • The ISP is fail-safe, in that if currents beyond its rating cause the device to fail, it will always fail as a short circuit, safely grounding the structure. Failure is non-eventful, and the device can be easily restored to service after factory rework. The ISP is even self-protected for steady-state AC current beyond the rating. Any failure of the polarization cell would result in an open-circuit, with no further safety grounding available for the structure or personnel.
  • Worker safety, environmental concerns, and maintenance issues are removed via the solid-state design of the ISP. Polarization cells contain a hazardous electrolyte.
  • Comprehensive field testing is available when an ISP has the optional Test Point, allowing the In-Situ Tester to perform a number of status checks, measurements, and force the ISP into various operating modes. Basic tests to confirm the status of the device can always be done with simple field equipment, such as a multimeter.
  • All anticipated system conditions have been factored into the logic design of the ISP, allowing it to be self-protected for certain conditions, and correctly operate and reset for all operations. The fail-safe nature is key for safety grounding of structures.
ISP
Quantity Weight Packaged Dimensions
1 96 39x13x11"

Note: For other ISP models or quantities, contact Dairyland for more information.