A power module for a cathodic protection system is provided having a switch-mode power circuit and a synchronous switch assembly. The method of the invention comprises rectifying an alternating utility power signal with a power transformer and switch assembly. The switch assembly is controlled by a phase control circuit to provide a selective controlled phase delay to provide a 0-100% range power signal to the load selectively operable in a constant current, constant voltage or off-potential manner.

Power supply for cathodic protection system

A cathodic protection monitoring system which provides IR drop free cathodic protection potential measurements which are indicative of the effectiveness of the cathodic protection system. The system measures the polarized potential between a reference electrode and a coupon subsequent to decoupling the coupon from the protected structure. The present invention controls the time or times at which the potential is measured in order to ensure that the potential is measured only after the polarized potential has achieved a relatively steady state value. More particularly, the cathodic protection monitoring system controllably measures the polarized potential after the potential has stabilized to the extent that there are no inductive or capacitive voltage spikes present, and before the coupon potential decays significantly due to depolarization. The system also can eliminate or reduce to an acceptable level the impact of telluric and other stray DC currents in the earth or structure metal path on the potential values measured.

Method and system for measuring the polarized potential of a cathodically protected structures substantially IR drop free

An automotive cathodic protection apparatus applies direct current to an integrated circuit timer and power controller, which generates timed output pulses An output charge storing capacitor connects the power source and timer to a vehicle body

Cathodic protection system using carbosil anodes

A method for detecting the polarized potential of a buried pipe which is cathodically protected by rectified alternating current impressed upon the pipe. Each rectified protection current is periodically pulsed to an off state (EOFF) for a precise pulse duration and pulse period which are integral multiples of the period of the alternating current. The potential between the pipe and a reference electrode at the test site is sampled and analyzed to detect the polarized potential. It is analyzed to find the area under the portion of the wave form during which no off pulses are present and to use that area to detect the on potential (EON). The area within the off pulses (A-F), after reactive spikes are eliminated, is subtracted from the on potential area to determine the IR drop potential (EIR). The IR drop potential (EIR) is then subtracted from the on potential (EON) and the difference is displayed as the polarized potential.

Measurement of the polarized potential of buried pipeline having impressed current cathodic protection

Method, system and apparatus for carrying out the cathodic protection of structures wherein evaluation of true current and true voltages at the counter electrode is carried out by an integration procedure which is timed in conjunction with the cross-over times of the originating a.c. input to the power source. The system also may employ an IR drop free potential measurement of a variety employing a reference electrode and a control which periodically turns off the fluctuating current drive to the working electrode for purposes of carrying out potential measurement from the reference electrode. To improve performance of the system, as well as the true current measuring features, difference networks are used to develop the difference between the signals of one channel, i.e. ground, and the parallel channel, i.e. positive, leading to the working and reference electrodes. With the arrangement, spurious noise phenomena are cancelled. The system also employs a hierarchal control system which operates in conjunction with a soft start procedure functioning to enhance system reliability.

Cathodic protection of structures

An electronic circuit for measuring the IR drop free potential of a cathodically protected structure includes a shunting transistor which is periodically pulsed on to shunt or electrically connect the output lines of a rectifier to force the voltage and current delivered to a structure being cathodically protected to zero. The reference cell potential is measured during this zero or sampling time and a minimum value detected by a detector circuit which holds the value until changed in successive sampling periods. The minimum reference cell potential is then compared to a voltage corresponding to a desired reference cell potential and the difference used to generate a firing voltage for SCRs in the rectifier and thereby control its output to achieve the desired level of cathodic protection.

Apparatus and method for measuring the IR drop free cathodic protection potential created by a rectifier and controlling rectifier operation to achieve a desired level thereof

John I. Garrett

Papers

Apparatus and method for measuring the IR drop free cathodic protection potential created by a rectifier and controlling rectifier operation to achieve a desired level thereof