Hydraulic control system having over-pressure protection

A method of operating a hydraulic control system, comprising:

• pressurizing a fluid with a pump;
• directing pressurized fluid from the pump to an actuator and draining fluid from the actuator to move the actuator;
• moving a main relief valve away from a closed position when a pressure of fluid at the actuator exceeds a first threshold pressure;
• and
• reducing a displacement of the pump after the main relief valve has moved away from the closed position when the pressure of the fluid at the actuator exceeds a second threshold pressure.

A machine, comprising:

• a frame;
• a work tool operatively connected to the frame;
• a tank;
• a plurality of pumps configured to draw fluid from the tank and pressurize the fluid;
• a plurality of actuators disposed between the frame and the work tool;
• at least one control valve configured to direct fluid from the plurality of pumps to the plurality of actuators and from the plurality of actuators to the tank to move the work tool;
• a main relief valve movable away from a closed position to pass pressurized fluid to the tank when a pressure of the fluid at the plurality of actuators exceeds a first threshold pressure;
• and
• a controller in communication with the plurality of pumps and configured to:
• selectively reduce a displacement of at least one of the plurality of pumps after the main relief valve has moved away from the closed position when the pressure of the fluid directed to at least one of the plurality of actuators exceeds a second threshold pressure;
• limit displacement reduction of the plurality of pumps based on the pressure of the fluid to 10% of a maximum flow rate;
• move the main relief valve to a fully opened position when the pressure of the fluid at the plurality of actuators reaches a third threshold pressure higher than the second threshold pressure;
• and
• inhibit displacement reduction of the plurality of pumps during a high-load mode of operation requested by an operator.