The protection circuit comprises two major components for Over Current (OC) and Over Voltage (OV). The nominal 'on state' resistance of OC device is of the order of 4 to 8 ohms which goes up to a few mega ohms when excess current flows through the loop/circuit. The OC device returns to normal after the line condition is restored. The Over Voltage device connected in parallel provides low impedance to high voltages beyond the rated voltage on a phone line (typical 250 V AC). This device can handle as high as 1000 Amperes short-term short circuit current (as per ITU-T K.21 standards). The Over Voltage device withstands Lightning voltage: 1.5KV - 36 KV with different wave-shapes. Lightning current: Up to 1000 Amperes with different wave-shapes (as per the ITU-T K.44 standards).
|Parameters||GDT Type Protection||COLOGICX LPU|
|OC, OV protection.||Glass fuse/ PTC and GDT||PTC, Thyristor based solid state technology|
|Device characteristic OC for 2 X I rated||Blows/acts with slow response time: 10sec||Self-Resetting with fast response time:
|OV||Hybrid device||Fold-back device, very low "ON state" Voltage, Compatible with existing MDFs.|
|Voltage dv/ dt rating||100 Volts/microsecond||400 Volts/ microsecond|
|Current Limit||250 milliamp fast blow fuse||120 milliamps, self resetting|
|Maintenance||Requires Maintenance||Maintenance free (Self restart after situation becomes normal)|
|Ageing||Performance degradation due to depletion effect in GDT||No performance degradation even after repetitive surges|
|Certification||Not mentioned||LPU has been Certified by Electrical Research and Development Association (ERDA), a Test and Calibration Laboratory approved by The Government of India
A. Lightning Parameter Tests as per ITU-T K.21 vide certificate no.: PHV/01/919 dated: 30/11/2001: Single Port Lightning Inherent Longitudinal Voltage Multiple Port Lightning Inherent Longitudinal Voltage Single Port Lightning Current
LPU-10 : 10 Lines protection system fitting on a 10 Port Krone Type MDF
IMPORTANT - A perfect 'Earth' connection to the LPU is essential for it to protect effectively. The Krone connectors must be well maintained and corrosion free and dust free. While fitting the LPU on to the Krone, please ensure that Line Side (as embossed on the plastic casing) should be on the Line side only.